Fermentation Strategy Research Articles

Optimizing Fermentation Strategies for Enhanced Tryptophan Production in Escherichia coli: Integrating Genetic and Environmental Controls for Industrial Applications

Tryptophan is an essential aromatic amino acid widely used in the pharmaceutical, agricultural, and feed industries. Microbial fermentation, mainly using Escherichia coli, has become the preferred method for its production due to sustainability and lower costs. Optimizing tryptophan production requires careful control of various fermentation parameters, including nutrients, pH, temperature, and dissolved oxygen (DO) levels. Glucose, as the primary carbon source, must be fed at controlled rates to avoid metabolic overflow, which leads to by-product accumulation and reduced production efficiency. Nitrogen sources, both organic (such as yeast extract) and inorganic (like ammonium), influence biomass growth and tryptophan yield, with ammonium levels requiring careful regulation to avoid toxic accumulation. Phosphate enhances growth but can lead to by-product formation if used excessively. pH is another critical factor, with an optimal range between 6.5 and 7.2, where enzyme activity is maximized. Temperature control promotes growth and production, particularly between 30 °C and 37 °C. High DO levels increase tryptophan titers by boosting the pentose phosphate pathway and reducing by-products like acetate. Furthermore, surfactants and supplements such as betaine monohydrate and citrate help alleviate osmotic stress and enhance precursor availability, improving production efficiency. Careful manipulation of these parameters allows for high-density cell cultures and significant tryptophan accumulation, making microbial fermentation competitive for large-scale production.

13 C-MFA helps to identify metabolic bottlenecks for improving malic acid production in Myceliophthora thermophila

BackgroundMyceliophthora thermophila has been engineered as a significant cell factory for malic acid production, yet strategies to further enhance production remain unclear and lack rational guidance. 13C-MFA (13C metabolic flux analysis) offers a means to analyze cellular metabolic mechanisms and pinpoint critical nodes for improving product synthesis. Here, we employed 13C-MFA to investigate the metabolic flux distribution of a high-malic acid-producing strain of M. thermophila and attempted to decipher the crucial bottlenecks in the metabolic pathways.ResultsCompared with the wild-type strain, the high-Malic acid-producing strain M. thermophila JG207 exhibited greater glucose uptake and carbon dioxide evolution rates but lower oxygen uptake rates and biomass yields. Consistent with these phenotypes, the 13C-MFA results showed that JG207 displayed elevated flux through the EMP pathway and downstream TCA cycle, along with reduced oxidative phosphorylation flux, thereby providing more precursors and NADH for malic acid synthesis. Furthermore, based on the 13C-MFA results, we conducted oxygen-limited culture and nicotinamide nucleotide transhydrogenase (NNT) gene knockout experiments to increase the cytoplasmic NADH level, both of which were shown to be beneficial for malic acid accumulation.ConclusionsThis work elucidates and validates the key node for achieving high malic acid production in M. thermophila. We propose effective fermentation strategies and genetic modifications for enhancing malic acid production. These findings offer valuable guidance for the rational design of future cell factories aimed at improving malic acid yields.

Multi-omics analysis of metabolic differences in rape bee pollen fermented by single and mixed lactic acid bacterial strains

Bee pollen is a nutrient-rich granule, but its hard cell wall limits the absorption of its nutrients by the human body. Fermenting bee pollen with lactic acid bacteria breaks down its cell wall and enhances its metabolite profile, improving nutrient availability. However, the differences in metabolites and cell wall disruption effects between mixed and single-strain fermentation have not been clarified. This study aimed to analyze the metabolites of Lactobacillus plantarum comprehensively fermented bee pollen (LPFP), Lactobacillus acidophilus fermented bee pollen (LAFP), and L. plantarum and L. acidophilus mixed fermented bee pollen (LMFP) using targeted and untargeted metabolomics as well as lipidomics, to explore the key metabolic pathways of LMFP. The results showed that under scanning electron microscopy (SEM), the cell wall of LMFP was more thoroughly disrupted. Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) and metabolic pathway enrichment analysis indicated that the degradation of flavonoids in LMFP was reduced, while the contents of total phenols, total flavonoids, rutin, and other polyphenols were significantly increased. Meanwhile, the metabolism of sucrose and amino acids in LMFP was enhanced, which might have contributed to the production of flavor compounds. Additionally, compared to LAFP and LPFP, triglycerides (TG) in LMFP increased by 8.14% and 9.85%, respectively, while the proportion of phosphatidylcholine (PC) decreased by 0.62% and 2.88%. Overall, this study presents a comprehensive metabolic profile of LAFP, LPFP, and LMFP, demonstrating how fermentation strategies affect cell wall disruption and metabolite diversity, laying a foundation for enhancing bee pollen's nutritional and functional properties.

Recent Trends in the Production and Recovery of Bioplastics Using Polyhydroxyalkanoates Copolymers

Polyhydroxyalkanoates (PHAs) are polyesters synthesized as a carbon and energy reserve material by a wide number of bacteria. These polymers are characterized by their thermoplastic properties similar to those of plastics derived from the petrochemical industry, such as polyethylene and polypropylene. PHAs are widely used in the medical field and have the potential to be used in other applications due to their biocompatibility and biodegradability. Among PHAs, P(3HB-co-3HV) copolymers are thermo-elastomeric polyesters that are typically soft and flexible with low to no crystallinity, which can expand the range of applications of these bioplastics. Several bacterial species, such as Cupriavidus necator, Azotobacter vinelandii, Halomonas sp. and Bacillus megaterium, have been successfully used for P(3HB-co-3HV) production, both in batch and fed-batch cultures using different low-cost substrates, such as vegetable and fruit waste. Nevertheless, in recent years, several fermentation strategies using other microbial models, such as methanotrophic bacterial strains as well as halophilic bacteria, have been developed in order to improve PHA production in cultivation conditions that are easily implemented on a large scale. This review aims to summarize the recent trends in the production and recovery of PHA copolymers by fermentation, including different cultivation modalities, low-cost raw materials, as well as downstream strategies that have recently been developed with the purpose of producing copolymers, such as P(3HB-co-3HV), with suitable mechanical properties for applications in the biomedical field.

Lactic acid bacteria sequential fermentation improves viable counts and quality of fermented apple juice via generating two logarithmic phases

This study investigated the impact of lactic acid bacteria (LAB) sequential fermentation on viable counts and apple juice quality. The optimal fermentation conditions were obtained by a step-by-step optimization process, including pH 4.5, temperature 37 °C, the second inoculation time 16 h, total fermentation time 40 h and fermentation sequence (first 21,805 + 21,828, second 20,241). Under the optimal conditions, sequential fermentation allowed LAB to experience two logarithmic phases, increasing viable counts to 1.38 × 108 CFU/mL, exceeding simultaneous fermentation for 24 h and 40 h by 4.10 × 107 CFU/mL and 5.40 × 107 CFU/mL, respectively. This process enhanced sugar utilization, yielding more lactic acid and polyphenols. Furthermore, sequential fermentation improved DPPH (71.71 %) and ABTS (84.79 %) scavenging rates, and enriched volatile compounds, particularly beta-Damascenone, potentially contributing to floral and richer apple flavor. Sequential fermentation also achieved optimal sensory acceptability. This study proposes a novel strategy for high-density LAB fermentation to produce high-quality apple juice.

Protein hydrolysates with ACE-I inhibitory activity from amaranth seeds fermented with Enterococcus faecium-LR9: Identification of peptides and molecular docking

One of the causes of hypertension is the activity of angiotensin-I converting enzyme (ACEI), making its inhibition a crucial strategy for controlling the disease. Protein hydrolysates are a known source of bioactive peptides that contribute to ACE-I inhibition. This study aims to evaluate the ACE-I inhibitory activity of amaranth seed hydrolysates after fermentation with Enterococcus faecium-LR9 and to compare it with Leuconostoc mesenteroides-18C6 and enzymatic hydrolysis (Alcalase®). The fermentation strategy with LR9 proved to be more effective in inhibiting ACE-I (79.1 ± 2.6 %) in vitro compared to 18C6 (68.0 ± 9.8 %) and enzymatic hydrolysis (69.4 ± 1.2 %). Consequently, these protein hydrolysates were subjected to in silico analysis, identifying 125 novel peptides. Bioinformatics and molecular docking analyses revealed 10 peptides with high ACE-I inhibitory potential. Among them, the IFQFPKTY and VIKPPSRAW peptides stood out. Therefore, E. faecium-LR9 is a promising strain for the release of bioactive peptides from seed storage proteins.

Identifying sesterterpenoids via feature-based molecular networking and small-scale fermentation.

Terpenoids are known for their diverse structures and broad bioactivities with significant potential in pharmaceutical applications. However, natural products with low yields are usually ignored in traditional chemical analysis. Feature-based molecular networking (FBMN) was developed recently to cluster compounds with similar skeletons, which can highlight trace amounts of unknown compounds. Fusoxypene A is a sesterterpene synthesized by Fusarium oxysporum fusoxypene synthase (FoFS) with a unique 5/6/7/3/5 ring system. In this study, the FoFS-containing biosynthetic gene cluster was identified from F. oxysporum FO14005, and an efficient FBMN-based strategy was established to characterize four new sesterterpenoids, fusoxyordienoid A-D (1-4), based on a small-scale fermentation strategy. A cytochrome P450 monooxygenase, FusB, was found to be involved in the functionalization of fusoxypene A at C-17 and C-24 and responsible for the hydroxylation of fusoxyordienoid A at C-1 and C-8. This study highlights the potential of FBMN as a powerful tool for the discovery and characterization of natural compounds with low abundance. KEY POINTS: Combined small-scale fermentation and FBMN for rapid discovery of fusoxyordienoids Characterization of four new fusoxyordienoids with 5/6/7/3/5 ring system Biosynthetic pathway elucidation via tandem expression and substrate feeding.

From Knallgas Bacterium to Promising Biomanufacturing Host: The Evolution of Cupriavidus necator.

The expanding field of synthetic biology requires diversification of microbial chassis to expedite the transition from a fossil fuel-dependent economy to a sustainable bioeconomy. Relying exclusively on established model organisms such as Escherichia coli and Saccharomyces cerevisiae may not suffice to drive the profound advancements needed in biotechnology. In this context, Cupriavidus necator, an extraordinarily versatile microorganism, has emerged as a potential catalyst for transformative breakthroughs in industrial biomanufacturing. This comprehensive book chapter offers an in-depth review of the remarkable technological progress achieved by C. necator in the past decade, with a specific focus on the fields of molecular biology tools, metabolic engineering, and innovative fermentation strategies. Through this exploration, we aim to shed light on the pivotal role of C. necator in shaping the future of sustainable bioprocessing and bioproduct development.

Scaled-up production and recovery of lipopeptide biosurfactant and its application for washing petroleum-contaminated drill cuttings

A simple and efficient fermentation strategy using chitosan-immobilized Bacillus subtilis GY19 was developed for large-scale lipopeptide production from waste glycerol and palm oil. When a fed-batch fermentation approach was employed, excessive foaming was minimized, while lipopeptide production was greater than that of conventional batch fermentation. When a 700L stirred tank fermenter with a 400L working volume was used, a lipopeptide concentration and yield of 7.55g/L and 0.190g/g of substrate, respectively, were achieved. The pilot-scale recovery process involved sequential bacterial cell removal via centrifugation, elimination of impurities through acidification of the cell-free broth, and partial purification and concentration of the lipopeptides via ultrafiltration. A 5kDa stabilized cellulose-based membrane maintained a constant permeate flux and resulted in 67.2% lipopeptide recovery. The concentrated lipopeptide retentate contained 16.8g/L lipopeptides and a surface tension of 28.82 mN/m. A biobased washing agent for the treatment of petroleum-contaminated drill cuttings was later formulated with the retentate and various vegetable oil-based surfactants via the simplex−lattice mixture design methodology. The mixture of 1% retentate and 4% fatty alcohol ethoxylate 5EO presented the greatest removal efficiency of 83.2% for drill cuttings containing 15% (w/w) total petroleum hydrocarbons. The formulation also mobilized petroleum hydrocarbons into a distinct free oil layer, which would be easy to separate and subsequently recycle. These findings demonstrate the scalability of the lipopeptide production and recovery process, while the biobased washing agent offers an environmentally friendly approach for petroleum remediation.

Improved fermentation strategies for enhancing polyhydroxybutyrate production from paper mill fiber rejects

Improved fermentation strategies for enhancing polyhydroxybutyrate production from paper mill fiber rejects

Transcriptional Downregulation of Methanol Metabolism Key Genes During Yeast Death in Engineered Pichia pastoris.

Pichia pastoris possesses the unique ability to utilize methanol as its sole carbon source, which makes it a proper host for producing various high-value-added products via metabolic engineering. Nevertheless, cell death has been observed during the fermentation of modified P. pastoris, with limited literature elucidating the underlying causes and mechanisms. Understanding the death mechanisms during methanol-based fermentation is crucial for optimizing fermentation strategies, enhancing the accumulation of target products, and reducing production costs. Here, we first sought to eliminate the potential causes of cell death during fermentation, such as inadequate inorganic salts and toxic by-product accumulation. The elimination of these potential causes was achieved efficiently utilizing the high-throughput fermentation equipment. Subsequently, we established a correlation between yeast cell death and the duration of the methanol metabolism period by monitoring the growth of the yeast at different fermentation stages. A critical revelation from this work came from analyzing the yeast's transcriptomic data at various stages of methanol metabolism. It was observed that a significant characteristic of yeast cell death during fermentation was the marked down-regulation of transcript levels of key enzymes involved in the methanol assimilation pathway and genes related to their biosynthesis process. The findings of this work are crucial for better understanding the causes and mechanisms of cell death for engineered P. pastoris during methanol-utilized fermentation.

Screening and characterization of indigenous Saccharomyces cerevisiae and non-Saccharomyces yeasts isolated from Sicilian vineyards

The use of Saccharomyces cerevisiae as starter cultures in winemaking is widespread in all over the world. However, a growing interest in exploring native non-Saccharomyces yeast species as co-starters has emerged, driven by their potential to enhance wine complexity and regional identity. The aim of the present study was to investigate indigenous yeasts from Sicily, to select novel strains with promising technological traits. A comprehensive screening of indigenous S. cerevisiae and non-Saccharomyces yeasts was conducted across seven locations in Sicily, including the unique volcanic zone of Mount Etna. A total of 95 yeast isolates were obtained and genetically characterized by RFLP-PCR and sequencing of 5.8S-ITS rDNA. Isolates were screened for oenological traits and the most promising, belonging to Starmerella bacillaris, Hanseniaspora uvarum, and Metschnikowia pulcherrima species, were used for single and sequential fermentations in synthetic must. Results revealed a remarkable diversity of physiological traits within and among the species, regarding stress tolerance, enzymatic activity and growth at different temperatures. Notably, isolates of H. uvarum and St. bacillaris exhibited great ethanol tolerance, and the latter also strong glycerol production. Furthermore, M. pulcherrima exhibited a wide range of aroma-related enzymatic activities, particularly beta-glucosidase. The remarkable diversity, the phenotypic traits of the indigenous yeasts, represents a promise for the improvement of innovative fermentation strategies and for the development of wine indigenous starters related with the region's terroir.

Strategic Use of Vegetable Oil for Mass Production of 5-Hydroxyvalerate-Containing Polyhydroxyalkanoate from δ-Valerolactone by Engineered Cupriavidus necator.

Although efforts have been undertaken to produce polyhydroxyalkanoates (PHA) with various monomers, the low yield of PHAs because of complex metabolic pathways and inhibitory substrates remains a major hurdle in their analyses and applications. Therefore, we investigated the feasibility of mass production of PHAs containing 5-hydroxyvalerate (5HV) using δ-valerolactone (DVL) without any pretreatment along with the addition of plant oil to achieve enough biomass. We identified that PhaCBP-M-CPF4, a PHA synthase, was capable of incorporating 5HV monomers and that C. necator PHB-4 harboring phaCBP-M-CPF4 synthesized poly(3HB-co-3HHx-co-5HV) in the presence of bean oil and DVL. In fed-batch fermentation, the supply of bean oil resulted in the synthesis of 49 g/L of poly(3HB-co-3.7 mol% 3HHx-co-5.3 mol%5HV) from 66 g/L of biomass. Thermophysical studies showed that 3HHx was effective in increasing the elongation, whereas 5HV was effective in decreasing the melting point. The contact angles of poly(3HB-co-3HHx-co-5HV) and poly(3HB-co-3HHx) were 109 and 98°, respectively. In addition, the analysis of microbial degradation confirmed that poly(3HB-co-3HHx-co-5HV) degraded more slowly (82% over 7 days) compared to poly(3HB-co-3HHx) (100% over 5 days). Overall, the oil-based fermentation strategy helped produce more PHA, and the mass production of novel PHAs could provide more opportunities to study polymer properties.

Investigation into the Production of Melanin from By-Products of Huangjiu Brewing.

Melanin is a high value bioproduct generated through the fermentation of Aureobasidium pullulans, playing a crucial role in various fields, including food, medicine, environmental protection, and materials science. However, its high production costs and low synthetic yields significantly limit its applications. Therefore, it is essential to identify high-yield strains, reduce production costs, and optimize fermentation strategies. In this study, a high melanin-yielding Aureobasidium pullulans 53LC7 was screened and identified, and the fermentation process was optimized based on melanin yield, color value, and pullulan yield. The results indicated that the melanin yield peaked at an initial pH of 6.0, temperature of 27 °C, fermentation time of 6.5 d, and inoculation quantity of 2.5%, achieving a melanin yield of 16.33 g/L. Subsequently, huangjiu lees, a byproduct of huangjiu production, was incorporated into the fermentation medium, resulting in a melanin yield of 5.91 g/L. This suggests that the Aureobasidium pullulans was not effectively utilizing huangjiu lees. To address this, we employed an adaptive evolution strategy, which increased the melanin yield to 8.72 g/L. The enhanced production was correlated with the expression of key genes, including FKS, PKS, and Cmr1. Finally, cellulase was utilized to convert the crude fibers in huangjiu lees, which were difficult to utilize, into usable substrates, while pullulanase was employed to minimize byproduct formation in the fermentation system, resulting in a melanin yield of 19.07 g/L. This study not only provides promising strains for further research but also offers valuable insights for resource production technologies.

Rewiring the reductive TCA pathway and glyoxylate shunt of Escherichia coli for succinate production from corn stover hydrolysate using a two-phase fermentation strategy

Succinate was found extensive applications in the food additives, pharmaceutical, and biopolymers industries. However, the succinate biosynthesis in E. coli required IPTG, lacked NADH, and produced high yields only under anaerobic conditions, unsuitable for cell growth. To overcome these limitations, the glyoxylate shunt and reductive TCA pathway were simultaneously enhanced to produce succinate in both aerobic and anaerobic conditions and achieve a high cell growth meanwhile. On this basis, NADH availability and sugars uptake were increased. Furthermore, an oxygen-dependent promoter was used to dynamically regulate the expression level of key genes of reductive TCA pathway to avoid the usage of IPTG. The final strain E. coli Mgls7-32 could produce succinate from corn stover hydrolysate without an inducer, achieving a titer of 72.8 g/L in 5 L bioreactor (1.2 mol/mol of total sugars). Those findings will aid in the industrial production of succinate.

High-yield production of 5-keto-D-gluconic acid via regulated fermentation strategy of Gluconobacter oxydans and its conversion to L-(+)-tartaric acid

Herein, we propose the production of 5-keto-D-gluconic acid (5KGA) by fermentation using Gluconobacter oxydans (G. oxydans) as the starting strain, from an initial concentration of 100 g/L glucose as substrate and the chemical conversion of 5KGA to L-(+)-tartaric acid (L-TA). The results show the efficacy and feasibility of two-stage pH (5.50→natural) linkage ventilation (0.5 vvm and 1.0 vvm, L/L/min) control of batch fermentation for 5KGA production. The final 5KGA yield of 100.2 g/L of 1.0 vvm is much higher than 0.5 vvm with an average productivity of 1.95 g/L/h. Changing the method of fermentation from batch to fed-batch can efficently prolong the high activity of G. oxydans for 5KGA production with an increased average productivity of 3.10 g/L/h, and the conversion rate of glucose to 5KGA is 92.50 %. The chemical conversion of 5KGA to L-TA catalyzed by metal ions in vitro indicates that the optimal catalyst is Cu2+ with a conversion rate of 35.09 % of 5KGA to L-TA. Our method can provide a practical and effective alternative for the industrial production of 5KGA and its conversion to L-TA.

Microbial Dynamics and Metabolite Profiles in Different Types of Salted Seafood (Jeotgal) During Fermentation.

Salted and fermented seafood (jeotgal) is known for its long shelf life and unique flavor. Despite the existence of various types of salted seafood, the factors influencing this quality have yet to be identified. These factors are essential for improving the quality of salted seafood, optimizing the fermentation process, and advancing the industrialization of fermented foods. Therefore, in this study, we explored microbial dynamics and changes in quality characteristics in three salted seafood items - salted anchovies (MJ), salted cutlass offal (GJ), and salted croakers (HJ), over a 24-month fermentation period. Distinct microbial community profiles, dominated by Tetragenococcus halophilus, Halanaerobium fermentans, and Chromohalobacter canadensis in MJ, GJ, and HJ, respectively, affect the metabolic pathways and the corresponding flavor profiles. The pH of all samples ranged from 5.7-6.0. The titratable acidity was highest in MJ at 1.4% and lowest in HJ at approximately 0.7%. Salinity was below 25% in all samples but slightly lower in MJ. Significant differences were observed in the amino acid, nucleotide, and overall metabolite profiles. MJ exhibited the highest amino acid and nitrogen-related factor levels, such as glutamic acid and hypoxanthine, enhancing flavor complexity. Correlation analysis revealed significant associations among the types, metabolites, and microbial communities. Microbial survival mechanisms in high-salt environments result in the production of unique metabolites, including umami and aroma components as well as precursors of biogenic amines, which can affect the overall quality of the final product. These differences were primarily influenced by the fish type rather than the fermentation time. Our findings provide foundational insights for enhancing fermentation strategies, improving product consistency, and advancing the industrial application of microbial management in seafood fermentation. This study not only fills a significant gap in the current understanding of fermented seafood but also outlines practical approaches for industry applications for the optimization of product quality.

Simultaneous Production of MK-7 and Iturin A by Bacillus velezensis ND.

Bacillus velezensis can produce various secondary metabolites, such as the antibacterial compound iturin A and the coagulation-promoting menaquinone-7 (MK-7). To enhance the economic feasibility of the fermentation process, a co-production strategy, involving the simultaneous production of MK-7 and iturin A by Bacillus velezensis ND, was investigated in this study. Firstly, the effects of cultivation temperature and initial pH on the synthesis of MK-7 and iturin A were investigated. Considering the co-production of iturin A and MK-7, the optimal temperature and pH were determined as 32°C and 7, respectively. Subsequently, important nutrients for the co-production process were investigated. It was observed that glycerol, soybean meal, yeast extract, and L-glutamate had a significant effect on the co-produce process. An optimal medium composed of glycerol (72.19mL L-1), L-glutamate (1.4g L-1), yeast extract (16.88g L-1), and soybean meal (130.95g L-1) was obtained by response surface methodology (RSM). This co-produce process was further scaled up in a biofilm reactor, and the maximum concentration of MK-7 and iturin A reached 46.88mg L-1 and 5.58g L-1, respectively. Finally, we established an effective method for separately extracting the two metabolites from the fermentation broth. The superiority of this co-production fermentation strategy demonstrates its significant potential for industrial production.

The impact of simultaneous inoculation with Torulaspora delbrueckii and Hanseniaspora uvarum combined with Saccharomyces cerevisiae on chemical and sensory quality of Sauvignon blanc wines.

Non-Saccharomyces yeasts have great potential in improving wine quality, showing personality characteristics, and highlighting the terroir of wine. In this study, we evaluated the impact of simultaneous inoculation with the non-Saccharomyces yeasts Torulaspora delbrueckii or (and) Hanseniaspora uvarum in combination with Saccharomyces cerevisiae (EC1118 or VL3) on the aromatic compounds and sensory quality of Sauvignon blanc wines. The growth of yeast groups in the alcoholic fermentation process was tracked using fluorescence in situ hybridization. The presence of non-Saccharomyces yeast notably impacted the distribution of S. cerevisiae and was related to the species of yeast. The co-fermentation of H. uvarum and S. cerevisiae improved the content of total esters, especially acetate esters. Simultaneous inoculation of T. delbrueckii or (and) H. uvarum significantly increased the content of total terpenes, especially linalool. Similar results were found for some higher alcohols and organic acids. Sensory evaluation showed that the wines mixed fermentation with H. uvarum had significantly tropical fruit aroma characteristics. Citrus and mineral notes, typical aroma characteristics of Sauvignon blanc wine, were enhanced by mixed fermentation strategies with T. delbrueckii or (and) H. uvarum and different S. cerevisiae. Hence, co-fermentation by T. delbrueckii or H. uvarum combined with S. cerevisiae could significantly improve the sensory quality of Sauvignon blanc wine.

High-yield magnetosome production of Magnetospirillum magneticum strain AMB-1 in flask fermentation through simplified processing and optimized iron supplementation.

Developing a simplified flask fermentation strategy utilizing magnetotactic bacterium AMB-1 and optimized iron supplementation for high-yield magnetosome production to address the challenges associated with magnetosome acquisition. A reliable processing for the pure culture of AMB-1 was established using standard laboratory consumables and equipment. Subsequently, the medium and iron supplementation were optimized to enhance the yield of AMB-1 magnetosomes. The mSLM supported higher biomass accumulation in flask fermentation, reaching an OD565 of ~ 0.7. The premixed solution of ferric quinate and EDTA-Fe (at a ratio of 0.5:0.5 and a concentration of 0.4mmol/L) stabilized Fe3+ and significantly increased the reductase activity of AMB-1. Flask fermentations with an initial volume of 15 L were then conducted employing the optimized fermentation strategy. After two rounds of iron and nutrient supplementation, the magnetosome yield reached 185.7 ± 9.5mg/batch (approximately 12mg/L), representing the highest AMB-1 flask fermentation yield to our knowledge. A flask fermentation strategy for high-yield magnetsome production was developed, eliminating the need for bioreactors and greatly simplifying the process of magnetosome acquisition.