Production Strains Research Articles

Bioprospecting of serratiopeptidase-producing bacteria from different sources

Anti-inflammatory enzymes have wide applications in the pharmaceutical industry. The objective of this study was to find new and efficient strains for the commercial production of serratiopeptidase enzyme. Vast number of samples were processed for the isolation of potent strains. The experimental treatment includes processing of twenty soil samples, silkworm gut, and sugarcane stem. The total protein and protease activity was estimated by Lowry’s method and casein hydrolysis. The HRBC stabilization assay was performed for finding the anti-inflammatory potential of all strains. The serratiopeptidase production was confirmed by HPLC with the standard. Molecular characterization of selected potent strains was done by 16S rDNA and confirmed the taxonomy. The one step rapid purification of serratiopeptidase was performed by Ultra three phase partitioning method. The clot lysis potential of the Serratia marcescens VS56 was observed by modified Holmstorm method. The results of the study revealed that among the 60 strains, 12 strains were protease-positive on skim milk agar plates and showed significant protease activity. All 12 strains were screened for serratiopeptidase using high-performance liquid chromatography (HPLC) and VS56, VS10, VS12 and VS18 showed a similar retention time (4.66 ± 0.10 min) with standard. The selected potent strain, Serratia marcescens VS56 showed a proteolytic activity of 21.30 units/mL and produced a total protein of 102 mg/mL. The HRBC suspension results also showed a percentage of 94.6 ± 1.00 protection, which was compared to the standard diclofenac. The clot lysis potential of Serratia marcescens VS56 was 53% in 4 h. Furthermore, the molecular weight of the protein was identified to confirm the presence of serratiopeptidase. The study hence contributed successfully to isolating, screening, and identifying a potent producer for serratiopeptidase from an environmental source. This inherent advantage of the strain will undoubtedly contribute much to the coco comm commercial production of serratiopeptidase in the near future.

Current and novel approaches in yeast cell death research.

The study of cell death mechanisms in fungi, particularly yeasts, has gained substantial interest in recent decades driven by the potential for biotechnological advancements and therapeutic interventions. Examples include the development of robust yeast strains for industrial fermentations and high-value compound production, novel food preservation strategies against spoilage yeasts, and the identification of targets for treating fungal infections in the clinic. In this review, we discuss a wide range of methods to characterize cellular alterations associated with yeast cell death, noting the advantages and limitations. We describe assays to monitor reversible events versus those that mark a commitment to cell death (point-of-no-return), as these distinctions are important to decipher the underlying regulatory mechanisms. Several well-known challenges remain, including the varied susceptibilities to death within a cell population and the delineation of detailed cell death mechanisms. The identification and characterization of morphologically distinct subsets of dying yeast cells within dynamic yeast populations provides opportunities to reveal novel vulnerabilities and survival mechanisms. Elucidating the intricacies of yeast regulated cell death (yRCD) will contribute to the advancement of scientific knowledge and foster breakthrough discoveries with broad-ranging implications.

307 Awardee Talk: Effects of dietary valerate glycerides on weanling piglet diarrhea and immunity

Abstract The use of various feed additives for their non-nutrient, immunomodulatory qualities is under investigation for application in swine production, especially during the post-weaning period. Butyrate (C4) is a known modulator of intestinal physiology, produced endogenously by commensal microbes and found in other organic sources. However, the understanding of the role of valerate (C5) as a feed additive for pigs has not been well-evaluated. Two experiments were conducted utilizing glycerides of butyrate or valerate as feed additives for weanling piglets under enterotoxigenic Escherichia coli (ETEC) infection conditions. In both experiments, daily diarrhea scores were recorded to monitor the frequency of diarrhea. The first pilot experiment utilized 20 weanling piglets (21 to 24 d of age) housed individually and assigned to either control diet, or control diet supplemented with 0.10% butyrate glycerides or 0.10% valerate glycerides. This experiment also aimed to establish a coinfection disease model, administering two strains of ETEC at a dose of 0.5 × 109 CFU/1.5 mL for each strain after a 7-d adaptation period (F4 and F18; two highly prevalent strains in swine production). Overall, piglets had significantly (P < 0.05) decreased frequency of diarrhea in either treatment group compared with control, suggesting similar modulatory effects by dietary valerate glycerides and butyrate glycerides. In addition, pigs fed valerate glycerides tended (P = 0.061) to have less neutrophils and had significantly (P < 0.05) less serum TNF-α on d 4 post-inoculation (PI). Moving forward, a full-scale experiment was performed using 60 weanling piglets (21 to 24 d of age) to further investigate the effect of dietary valerate glycerides on piglet health under ETEC F18 infection conditions. Treatments included nursery basal diet (control), 0.075% or 0.10% monovalerin, or 0.1% trivalerin added to control. Pigs fed 0.1% trivalerin exhibited significantly (P < 0.05) reduced frequency of diarrhea and fecal shedding of ETEC F18. Serum samples were collected throughout the experimental period and six replicate pigs per treatment group were sacrificed on d 7 PI to collect intestinal samples for morphological analysis and intestinal mucosa RT-qPCR analysis. Pigs fed trivalerin had reduced (P < 0.05) serum TNF-α on d 0 before inoculation and d 6 PI compared with pigs in control. The mRNA expression of TNFA in ileal mucosa from pigs fed 0.1% monovalerin tended (P < 0.10) to be lower compared with control. In addition, ZO1 mRNA expression tended (P < 0.10) to be increased in jejunal mucosa from pigs fed 0.1% trivalerin. Overall, the second experiment indicated that dietary supplementation of valerate glycerides reduced diarrhea and fecal shedding of ETEC F18 in piglets infected with ETEC. In conclusion, both experiments provide evidence in support of supplementing 0.075 or 0.10% valerate glycerides could enhance disease resistance of weanling piglets experiencing ETEC-associated diarrhea.

Development of an engineered Bacillus subtilis strain for antibiotic-free sucrose isomerase production.

Sucrose isomerase (SIase) catalyzes the hydrolysis and isomerization of sucrose into isomaltulose, a functional sugar extensively used in the food industry. However, the lack of safe and efficient heterologous expression systems for SIase has constrained its production and application. In this study, an engineered Bacillus subtilis strain for antibiotic-free SIase production was developed via a food-grade expression system. First, the B. subtilis strain TEA was modified through the CRISPR/Cas9 system, resulting in a mutant strain TEA4, which exhibited enhanced capabilities for recombinant protein expression. For efficient and safe production of SIase, different constitutive and inducible promoters were evaluated. The maltose-inducible promoter Poglv was found to have an extracellular SIase activity of 21.7 UmL-1 in engineered strain TEA4. Subsequent optimization of the culture medium further increased SIase activity to 26.4 UmL-1 during shake flask cultivation. Eventually, using the crude enzyme solution of the engineered strain in biotransformation reactions resulted in a high yield of isomaltulose under high concentrations sucrose, achieving a maximum yield of 83.1%. These findings demonstrated an engineered B. subtilis strain for antibiotic-free SIase production, paving the way for its scale-up industrial production and application.

Alicyclobacillus spp. in fruit-based products: Isolation, identification, quantitative assessment (SPME/GC–MS) of spoilage compounds and spore's resistance to thermal shocks

Alicyclobacillus spp. is the cause of great concern for the food industry due to their spores' resistance (thermal and chemical) and the spoilage potential of some species. Despite this, not all Alicyclobacillus strains can spoil fruit juices. Thus, this study aimed to identify Alicyclobacillus spp. strains isolated from fruit-based products produced in Argentina, Brazil, and Italy by DNA sequencing. All Alicyclobacillus isolates were tested for guaiacol production by the peroxidase method. Positive strains for guaiacol production were individually inoculated at concentration of 103 CFU/mL in 10 mL of orange (pH 3.90) and apple (pH 3.50) juices adjusted to 11°Brix, following incubation at 45 °C for at least 5 days to induce the production of the following spoilage compounds: Guaiacol, 2,6-dichlorophenol (2,6-DCP) and 2,6-dibromophenol (2,6-DBP). The techniques of micro-solid phase extraction by headspace (HS-SPME) and gas-chromatography with mass spectrometry (GC–MS) were used to identify and quantify the spoilage compounds. All GC–MS data was analyzed by principal component analysis (PCA). The effects of different thermal shock conditions on the recovery of Alicyclobacillus spores inoculated in orange and apple juice (11°Brix) were also tested. A total of 484 strains were isolated from 48 brands, and the species A. acidocaldarius and A. acidoterrestris were the most found among all samples analyzed. In some samples from Argentina, the species A. vulcanalis and A. mali were also identified. The incidence of these two main species of Alicyclobacillus in this study was mainly in products from pear (n = 108; 22.3 %), peach (n = 99; 20.5 %), apple (n = 86; 17.8 %), and tomato (n = 63; 13 %). The results indicated that from the total isolates from Argentina (n = 414), Brazil (n = 54) and Italy (n = 16) were able to produce guaiacol: 107 (25.8 %), 33 (61.1 %) and 13 (81.2 %) isolates from each country, respectively. The PCA score plot indicated that the Argentina and Brazil isolates correlate with higher production of guaiacol and 2,6-DCP/2,6-DBP, respectively. Heatmaps of cell survival after heat shock demonstrated that strains with different levels of guaiacol production present different resistances according to spoilage ability. None of the Alicyclobacillus isolates survived heat shocks at 120 °C for 3 min. This work provides insights into the incidence, spoilage potential, and thermal shock resistance of Alicyclobacillus strains isolated from fruit-based products.

Safety and efficacy of a feed additive consisting of muramidase produced with Trichoderma reeseiDSM 32338 (Balancius™) for laying hens (DSM nutritional products).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of muramidase produced with Trichoderma reesei DSM 32338 (Balancius™) as a feed additive for laying hens. The additive is already authorised as a zootechnical additive (functional group: other zootechnical additives) for chickens, turkeys and minor poultry species for fattening or reared for breeding, and for weaned piglets. The enzyme is produced by fermentation with a genetically modified strain of Trichoderma reesei; viable cells of the production strain and its recombinant DNA were not detected in the additive. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive does not give rise to safety concerns regarding the genetic modification of the production strain. Based on the data available from a sub-chronic oral toxicity study, the Panel concluded that the additive is safe for laying hens at the maximum recommended level of 60,000 LSU(F) (muramidase activity units)/kg feed. The Panel also concluded that the additive is safe for the consumers and the environment. The liquid formulation of the additive is considered not irritant to the skin or eyes. The solid formulation of the additive is considered not irritant to the skin. The Panel cannot conclude on the potential of the additive (both formulations) to be a dermal sensitiser or on the potential of the solid formulation to be irritant to the eyes. Due to the proteinaceous nature, both forms of the additive should be considered respiratory sensitisers. The additive has the potential to be efficacious as a zootechnical additive for laying hens at 30,000 LSU(F)/kg feed.

Harnessing Nature's Arsenal: Investigating the Antibacterial Efficacy of Commercial Essential Oils against Staphylococcus Strains Isolated from Poultry Meat.

Pathogens prevalent in the food supply chain provide a significant worldwide risk to both human health and the economy. Poultry meat, a staple in global diets, serves as a reservoir for bacterial contamination. Staphylococcus, a gram-positive bacterium belonging to family Staphylococcaceae has been identified as a potential causative agent of food borne illnesses. The presence of antibiotic-resistant Staphylococcus strains in poultry products raises concerns about the transmission of resistance genes through the food chain, necessitating thorough investigations into alternative antimicrobial agents for effective bacterial control. Essential oils (EOs) hold profound importance in terms of their known and potential application. This study focuses on the evaluation of commercial essential oils and their effectiveness against Staphylococcus strains isolated from poultry meat. Briefly, 150 raw chicken meat samples were collected, and Staphylococcus spp. was identified based on morphological and cultural characteristics. Antibiogram analysis and essential oils activity was determined by disc diffusion and agar well diffusion assay respectively. Results showed that 27 (18%) samples tested positive for Staphylococcus spp, out of which S. aureus was identified in 25 isolates (16.66%). The antibiogram profile reveals that three antibiotics namely, gentamicin, vancomycin and ciprofloxacin were the most effective antibiotics showing sensitivity against 74.07%, 70.37% and 62.96% of the isolates respectively. Moreover, amongst the tested essential oils cinnamon oil and clove oil exhibited the highest antimicrobial activities ZOI ranges from 19-41mm and 19-33 mm respectively. While focusing on the evaluation of antimicrobial activity of essential oils, the study endeavors to aid in development of sustainable strategies for mitigating bacterial contamination in the food industry.

The Value of Indigenous <i>Saccharomyces cerevisiae</i> Strains as Useful Enzymes Producers: A Systematic Review

This systematic review has focused on the selection and characterization of indigenous Saccharomyces cerevisiae strains for enzymes' production obtained from the fermentation process. The primary studies assessed have demonstrated that indigenous S. cerevisiae strains produce a wide range of enzymes during fermentation. These strains have shown different characteristics and were isolated from various locations, including those belonging to the main components of the wine production chain. The research methodology applied to find primary studies about the optimal conditions for enzyme production was effective and identified a wide range of enzyme classes. Cultivation media amended with natural or synthetic inducer substrates were found to be suitable carbon and/or nitrogen sources for producing enzymes of interest in plate-based screening. In submerged fermentation studies, the use of agro-industrial residues has been identified as a relevant carbon source for microbe development and metabolism. For the indigenous S. cerevisiae strains, the majority of the enzymes found belong to the glucosidases and hydrolases classes. Due to the activity of these enzymes, yeasts have been traditionally used in classic biotechnological applications, particularly in the process of alcoholic fermentations. Those enzymes are responsible for producing metabolites (such as aromatic compounds) that contribute to the desirable aroma and/or taste during the fermentation of wine, as well as other fermented or distilled beverages. The methods used for enzyme screening were of quantitative and/or qualitative nature and were carried out under acidic pH conditions (3.5-6.5) and at temperatures of 28-35 ℃. The results of this systematic review have shown that the enzymes from indigenous S. cerevisiae are highly relevant in various biotechnological applications, particularly in the food industry. Conclusions and future perspectives of our findings were discussed in terms of potential developments of novel application methods of the indigenous yeasts and their enzymes in agriculture and industry.

Characterization of Escherichia coli Strains for Novel Production of Plasmodium ovale Lactate Dehydrogenase

Malaria is one of the most prevalent diseases worldwide with high incidence and mortality. Among the five species that can infect humans, Plasmodium ovale morphologically resembles P. vivax, resulting in misidentification and confusion in diagnosis, and is responsible for malarial disease relapse due to the formation of hypnozoites. P. ovale receives relatively less attention compared to other major parasites, such as P. falciparum and P. vivax, primarily due to its lower pathogenicity, mortality rates, and prevalence rates. To efficiently produce lactate dehydrogenase (LDH), a major target for diagnosing malaria, this study used three Escherichia coli strains, BL21(DE3), BL21(DE3)pLysS, and Rosetta(DE3), commonly used for recombinant protein production. These strains were characterized to select the optimal strain for P. ovale LDH (PoLDH) production. Gene cloning for recombinant PoLDH production and transformation of the three strains for protein expression were performed. The optimal PoLDH overexpression and washing buffer conditions in nickel-based affinity chromatography were established to ensure high-purity PoLDH. The yields of PoLDH expressed by the three strains were as follows: BL21(DE3), 7.6 mg/L; BL21(DE3)pLysS, 7.4 mg/L; and Rosetta(DE3), 9.5 mg/L. These findings are expected to be highly useful for PoLDH-specific diagnosis and development of antimalarial therapeutics.

Scalable protein production by Komagataella phaffii enabled by ARS plasmids and carbon source-based selection

BackgroundMost recombinant Komagataella phaffii (Pichia pastoris) strains for protein production are generated by genomic integration of expression cassettes. The clonal variability in gene copy numbers, integration loci and consequently product titers limit the aptitude for high throughput applications in drug discovery, enzyme engineering or most comparative analyses of genetic elements such as promoters or secretion signals. Circular episomal plasmids with an autonomously replicating sequence (ARS), an alternative which would alleviate some of these limitations, are inherently unstable in K. phaffii. Permanent selection pressure, mostly enabled by antibiotic resistance or auxotrophy markers, is crucial for plasmid maintenance and hardly scalable for production. The establishment and use of extrachromosomal ARS plasmids with key genes of the glycerol metabolism (glycerol kinase 1, GUT1, and triosephosphate isomerase 1, TPI1) as selection markers was investigated to obtain a system with high transformation rates that can be directly used for scalable production processes in lab scale bioreactors.ResultsIn micro-scale deep-well plate experiments, ARS plasmids employing the Ashbya gossypii TEF1 (transcription elongation factor 1) promoter to regulate transcription of the marker gene were found to deliver high transformation efficiencies and the best performances with the reporter protein (CalB, lipase B of Candida antarctica) for both, the GUT1- and TPI1-based, marker systems. The GUT1 marker-bearing strain surpassed the reference strain with integrated expression cassette by 46% upon re-evaluation in shake flask cultures regarding CalB production, while the TPI1 system was slightly less productive compared to the control. In 5 L bioreactor methanol-free fed-batch cultivations, the episomal production system employing the GUT1 marker led to 100% increased CalB activity in the culture supernatant compared to integration construct.ConclusionsFor the first time, a scalable and methanol-independent expression system for recombinant protein production for K. phaffii using episomal expression vectors was demonstrated. Expression of the GUT1 selection marker gene of the new ARS plasmids was refined by employing the TEF1 promoter of A. gossypii. Additionally, the antibiotic-free marker toolbox for K. phaffii was expanded by the TPI1 marker system, which proved to be similarly suited for the use in episomal plasmids as well as integrative expression constructs for the purpose of recombinant protein production.

Food waste as a raw material for production of polyhydroxyalkanoates: State and prospects

The growing problem of environmental pollution by plastic leads to the search not only for the most promising biodegradable polymer, but also for optimal raw materials for its production. Polyhydroxyalkanoates (PHA) — biodegradable polymers with physical and mechanical properties close to traditional plastics — are considered a potential solution to this problem. The production of PHA can be organized according to the principles of circular bioeconomy through biotechnological processing of secondary raw materials to produce a product with added value. However, an important component of the expansion of PHA production is the need to find the most promising secondary raw materials for its production. The PHA market in Russia and the global market have been analyzed, highlighting the demand in the packaging and food industries, biomedicine and agro- industry as the fundamental factor for the growth of PHA production. Bibliographic analysis using the PRISMA scheme and VOSviewer program allowed identifying three main directions of PHA research: search for optimal secondary raw materials among food waste, analysis of challenges in PHA production, and the ecological and economic effects of its implementation. Promising types of secondary raw materials have been revealed: vegetable oil production waste, fruit and vegetable process- ing waste, dairy whey, sugar and starch industry waste, spent coffee grounds and coffee oils extracted from them. Advantages and disadvantages of using secondary raw materials, options for improving their use in the production of PHA, and the main strains-producers were determined. To optimize the cost and processes of PHA production, further studies of food waste are required, aimed at developing approaches to increase the polymer yield, including through the use of secondary raw material preparation processes, and the search for the most productive strains synthesizing PHA.

Application of multiple strategies to enhance oleanolic acid biosynthesis by engineered Saccharomyces cerevisiae

Oleanolic acid and its derivatives are widely used in the pharmaceutical, agricultural, cosmetic and food industries. Previous studies have shown that oleanolic acid production levels in engineered cell factories are low, which is why oleanolic acid is still widely extracted from traditional medicinal plants. To construct a highly efficient oleanolic acid production strain, rate-limiting steps were regulated by inducible promoters and the expression of key genes in the oleanolic acid synthetic pathway was enhanced. Subsequently, precursor pool expansion, pathway refactoring and diploid construction were considered to harmonize cell growth and oleanolic acid production. The multi-strategy combination promoted oleanolic acid production of up to 4.07 g/L in a 100 L bioreactor, which was the highest level reported.

Nutrients recovery from dairy wastewater by Chlorella vulgaris and comparison of the lipid's composition with various chlorella strains for biodiesel production.

Microalgae biomass is regarded as a promising feedstock for biodiesel production. The biomass lipid content and fatty acids composition are among the main selective criteria when screening microalgae strains for biodiesel production. In this study, three strains of Chlorella microalgae (C. kessleri, C. sorokiniana, C. vulgaris) were cultivated nutrient media with different nitrogen contents, and on a medium with the addition of dairy wastewater. Moreover, microalgae grown on dairy wastewater allowed the removal of azote and phosphorous. The removal efficiency of 90%, 53% and 95% of ammonium nitrogen, total nitrogen and phosphate ions, respectively, were reached. The efficiency of wastewater treatment from inorganic carbon was 55%, while the maximum growth of biomass was achieved. All four samples of microalgae had a similar fatty acid profile. Palmitic acid (C16:0) was the most abundant saturated fatty acid (SFA), and is suitable for the production of biodiesel. The main unsaturated fatty acids (UFA) present in the samples were oleic acid (C18:1 n9); linoleic acid (C18:2 n6) and alpha-linolenic acid (C18:3 n3), which belong to omega-9, omega-6, omega-3, respectively.

Establishment of low-cost production platforms of polyhydroxyalkanoate bioplastics from Halomonas cupida J9.

Microbial production of polyhydroxyalkanoate (PHA) is greatly restricted by high production cost arising from high-temperature sterilization and expensive carbon sources. In this study, a low-cost PHA production platform was established from Halomonas cupida J9. First, a marker-less genome-editing system was developed in H. cupida J9. Subsequently, H. cupida J9 was engineered to efficiently utilize xylose for PHA biosynthesis by introducing a new xylose metabolism module and blocking xylonate production. The engineered strain J9UΔxylD-P8xylA has the highest PHA yield (2.81 g/L) obtained by Halomonas with xylose as the sole carbon source so far. This is the first report on the production of short- and medium-chain-length (SCL-co-MCL) PHA from xylose by Halomonas. Interestingly, J9UΔxylD-P8xylA was capable of efficiently utilizing glucose and xylose as co-carbon sources for PHA production. Furthermore, fed-batch fermentation of J9UΔxylD-P8xylA coupled to a glucose/xylose co-feeding strategy reached up to 12.57 g/L PHA in a 5-L bioreactor under open and unsterile condition. Utilization of corn straw hydrolysate as the carbon source by J9UΔxylD-P8xylA reached 7.0 g/L cell dry weight (CDW) and 2.45 g/L PHA in an open fermentation. In summary, unsterile production in combination with inexpensive feedstock highlights the potential of the engineered strain for the low-cost production of PHA from lignocellulose-rich agriculture waste.

Impact of irradiance and inorganic carbon availability on heterologous sucrose production in Synechococcus elongatus PCC 7942.

Cyanobacteria have been proposed as a potential alternative carbohydrate feedstock and multiple species have been successfully engineered to secrete fermentable sugars. To date, the most productive cyanobacterial strains are those designed to secrete sucrose, yet there exist considerable differences in reported productivities across different model species and laboratories. In this study, we investigate how cultivation conditions (specifically, irradiance, CO2, and cultivator type) affect the productivity of sucrose-secreting Synechococcus elongatus PCC 7942. We find that S. elongatus produces the highest sucrose yield in irradiances far greater than what is often experimentally utilized, and that high light intensities are tolerated by S. elongatus, especially under higher density cultivation where turbidity may attenuate the effective light experienced in the culture. By increasing light and inorganic carbon availability, S. elongatus cscB/sps produced a total of 3.8 g L-1 of sucrose and the highest productivity within that period being 47.8 mg L-1 h-1. This study provides quantitative description of the impact of culture conditions on cyanobacteria-derived sucrose that may assist to standardize cross-laboratory comparisons and demonstrates a significant capacity to improve productivity via optimizing cultivation conditions.

Biosynthesis of Hesperetin, Homoeriodictyol, and Homohesperetin in a Transcriptomics-Driven Engineered Strain of Streptomyces albidoflavus.

Flavonoids exhibit various bioactivities including anti-oxidant, anti-tumor, anti-inflammatory, and anti-viral properties. Methylated flavonoids are particularly significant due to their enhanced oral bioavailability, improved intestinal absorption, and greater stability. The heterologous production of plant flavonoids in bacterial factories involves the need for enough biosynthetic precursors to allow for high production levels. These biosynthetic precursors are malonyl-CoA and l-tyrosine. In this work, to enhance flavonoid biosynthesis in Streptomyces albidoflavus, we conducted a transcriptomics study for the identification of candidate genes involved in l-tyrosine catabolism. The hypothesis was that the bacterial metabolic machinery would detect an excess of this amino acid if supplemented with the conventional culture medium and would activate the genes involved in its catabolism towards energy production. Then, by inactivating those overexpressed genes (under an excess of l-tyrosine), it would be possible to increase the intracellular pools of this precursor amino acid and eventually the final flavonoid titers in this bacterial factory. The RNAseq data analysis in the S. albidoflavus wild-type strain highlighted the hppD gene encoding 4-hydroxyphenylpyruvate dioxygenase as a promising target for knock-out, exhibiting a 23.2-fold change (FC) in expression upon l-tyrosine supplementation in comparison to control cultivation conditions. The subsequent knock-out of the hppD gene in S. albidoflavus resulted in a 1.66-fold increase in the naringenin titer, indicating enhanced flavonoid biosynthesis. Leveraging the improved strain of S. albidoflavus, we successfully synthesized the methylated flavanones hesperetin, homoeriodictyol, and homohesperetin, achieving titers of 2.52 mg/L, 1.34 mg/L, and 0.43 mg/L, respectively. In addition, the dimethoxy flavanone homohesperetin was produced as a byproduct of the endogenous metabolism of S. albidoflavus. To our knowledge, this is the first time that hppD deletion was utilized as a strategy to augment the biosynthesis of flavonoids. Furthermore, this is the first report where hesperetin and homoeriodictyol have been synthesized from l-tyrosine as a precursor. Therefore, transcriptomics is, in this case, a successful approach for the identification of catabolism reactions affecting key precursors during flavonoid biosynthesis, allowing the generation of enhanced production strains.

Reprogramming the Metabolism of Yeast for High-Level Production of Miltiradiene.

Miltiradiene serves as a crucial precursor in the synthesis of various high-value abietane-type diterpenes, exhibiting diverse pharmacological activities. Previous efforts to enhance miltiradiene production have primarily focused on the mevalonate acetate (MVA) pathway. However, limited emphasis has been placed on optimizing the supply of acetyl-CoA and NADPH. In this study, we constructed a platform yeast strain for miltiradiene production by reinforcing the biosynthetic pathway of geranylgeranyl diphosphate (GGPP) and acetyl-CoA, and addressing the imbalance between the supply and demand of the redox cofactor NADPH within the cytoplasm, resulting in an increase in miltiradiene yield to 1.31 g/L. Furthermore, we conducted modifications to the miltiradiene synthase fusion protein tSmKSL1-CfTPS1. Finally, the comprehensive engineering strategies and protein modification strategies culminated in 1.43 g/L miltiradiene in the engineered yeast under shake flask culture conditions. Overall, our work established efficient yeast cell factories for miltiradiene production, providing a foothold for heterologous biosynthesis of abietane-type diterpenes.

Safety and efficacy of a feed additive consisting of l-tryptophan (produced with Escherichia coliCGMCC 7.460) for all animal species (Kempex Holland B.V.).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of the feed additive consisting of l-tryptophan produced by fermentation with Escherichia coli CGMCC 7.460 when used as a nutritional additive in feed and water for drinking for all animal species and categories. The production strain is not genetically modified. Viable cells of the production strain were not detected in the final additive. The additive does not give rise to any safety concern regarding the production strain. The use of l-tryptophan (≥ 98%) produced with E. coli CGMCC 7.460 to supplement feed is safe for non-ruminant species. There may be a risk for an increased production of toxic metabolites when unprotected tryptophan is used in ruminants. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) has concerns on the safety of the simultaneous oral administration of l-tryptophan via water for drinking and feed due to possible amino acid imbalances and hygienic reasons. The use of l-tryptophan produced with E. coli CGMCC 7.460 in animal nutrition raises no safety concerns to consumers of animal products and to the environment. In the absence of data, the FEEDAP Panel cannot conclude on the potential of the additive to be irritant to skin or eyes, or on its potential to be a dermal sensitiser. The endotoxin activity of the additive in combination with the high dusting potential may represent a risk of exposure by inhalation to endotoxins for users. The additive l-tryptophan is regarded as an effective source of the amino acid l-tryptophan for all non-ruminant species. To be as efficacious in ruminants as in non-ruminants, it should be protected from ruminal degradation.

Safety and efficacy of a feed additive consisting of l-isoleucine produced with Corynebacterium glutamicumCGMCC 20437 for all animal species (Eppen Europe SAS).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of l-isoleucine produced by fermentation with Corynebacterium glutamicum CGMCC 20437 as a nutritional feed additive for use in feed and in water for drinking for all animal species. The production strain is non-genetically modified, qualifies for the QPS approach to safety assessment when used for production purposes, is susceptible to the relevant antibiotics and contains no antimicrobial resistance genes of concern. No viable cells of the production strain were detected in the final product. The additive does not give rise to any safety concern regarding the production strain. l-Isoleucine produced by fermentation with Corynebacterium glutamicum CGMCC 20437 is considered safe for the target species, the consumer and the environment. Regarding the use in water, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) reiterates its concerns over the safety for the target species of l-isoleucine administered simultaneously via water for drinking and feed owing to the risk of nutritional imbalances and hygienic reasons. In the absence of data, the FEEDAP Panel is not in a position to conclude on the potential of l-isoleucine produced by fermentation with Corynebacterium glutamicum CGMCC 20437 to be irritant to skin and/or eyes, or as a dermal sensitiser. Due to the high dusting potential, exposure by inhalation is likely. l-Isoleucine produced by fermentation with Corynebacterium glutamicum CGMCC 20437 is considered as an efficacious source of the essential amino acid l-isoleucine for non-ruminant animal species. For the supplemental l-isoleucine to be as efficacious in ruminants as in non-ruminant species, it would require protection against degradation in the rumen.

Safety and efficacy of a feed additive consisting of vitamin B12 (cyanocobalamin) produced by fermentation with Ensifer adhaerensCGMCC 21299 for all animal species (NHU Europe GmbH).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of vitamin B12 (cyanocobalamin) produced by fermentation with a non-genetically modified strain of Ensifer adhaerens (CGMCC 21299), when used as a nutritional additive for all animal species. No viable cells or DNA of the production strain were detected in the additive. Therefore, cyanocobalamin produced by fermentation with E. adhaerens CGMCC 21299 does not raise safety concerns as regards to the production strain. The Panel on Additives and Products or Substances used in Animal Feed concluded that cyanocobalamin produced by fermentation with E. adhaerens CGMCC 21299 is considered safe for all animal species, for the consumers and the environment. Due to the presence of nickel, the additive is considered a skin and respiratory sensitiser. Inhalation and dermal exposure are considered a risk. Due to the lack of data, the Panel could not conclude on the potential of the additive to be an eye irritant. Cyanocobalamin produced by fermentation with E. adhaerens CGMCC 21299 is effective in meeting animal's nutritional requirements when administered via feed.