Mixed Carbon Sources Research Articles

Efficient Production of Bacterial Cellulose Using Komagataeibacter sucrofermentans on Sustainable Feedstocks.

The production of bacterial cellulose (BC) has indeed garnered global attention due to its versatile properties and applications. Despite potential benefits, the challenges like low productivity, high fermentation costs, and expensive culture media hinder its industrialization. Utilizing low-cost substrates, especially waste streams, can help address the challenges. In this study, waste feedstocks such as restaurant leftovers, oranges, and grapefruit from canteens and supermarkets were valorized for BC production by Komagataeibacter sucrofermentans. Orange juice is a fascinating substrate with a highest concentration of 20.6 g/L and productivity of 2.05 g/L/d. Using HS medium with supplementary ions, organic acids, ethanol, and various carbon sources is a strategic approach for enhancing BC production. The study reveals that the addition of organic acids or ethanol moderately increased BC production, while ions inhibit BC synthesis, highlighting the complex interplay between various cultivation medium components. Additionally, fermentation with K. sucrofermentans using single and mixed carbon sources was conducted to elucidate the potential metabolic mechanism of BC production. Through alkaline treatment and drying in a 30 °C incubator, we produced the highest quality BC with 92.09 % crystallinity. Overall, the study enhances BC production knowledge and provides green and sustainable strategies for fermentative BC production.

Mechanisms of secondary carbonate precipitation on felsic, intermediate and mafic igneous rocks: a case study for NW Scotland

Silicate weathering is a natural regulator of atmospheric carbon dioxide (CO 2 ), where the majority of carbonate is stored in the oceans. In some instances, carbonates may form via bedrock weathering in terrestrial landscapes, but this is commonly noted in ultramafic rock owing to its desirable mineralogy. In NW Scotland, carbonate minerals surround felsic, intermediate and mafic igneous bedrock. Their abundance suggests that these rocks could potentially be targeted for carbonation, given the absence of other known cation sources nearby. We present geochemical and mineralogical data for bedrock samples and mineralogy and stable carbon and oxygen isotope data for the carbonate samples. Whole-rock geochemistry demonstrates that major abundances of CaO and MgO are present in the bedrock samples and would be sourced from plagioclase and pyroxene, which are target minerals for CO 2 mineralization. The stable carbon and oxygen isotope data demonstrate that there are probably mixed carbon sources (atmospheric and organic), and other environmental factors including temperature, CO 2 degassing or evaporation and nearby waters influence the isotopic composition. Results suggest that rocks traditionally overlooked in CO 2 mineralization studies have the potential to serve as a feedstock for carbonation, given the abundance of secondary carbonates found in NW Scotland.

Eco-friendly production and probiotic purification of agarose degradation products: Oligosaccharides and 3,6-anhydro-L-galactose

Algal biomass offers a solution to global resource scarcity, with agarose, a key component of Gelidium amansii, containing valuable products like oligosaccharides and 3,6-anhydro-L-galactose. However, current purification methods limit their commercial viability. In this study, we utilized gel filtration chromatography to purify agaro-oligosaccharides and neoagaro-oligosaccharides with varying degrees of polymerization, achieving a novel purification of odd-numbered neoagaro-oligosaccharides. Additionally, by fermenting a mixture of 3,6-anhydro L-galactose and D-galactose with six probiotics, our results demonstrate that five probiotics—Lactobacillus plantarum, Bifidobacterium adolescentis, Streptococcus thermophilus, Lactobacillus acidophilus, and Lactobacillus rhamnosus effectively utilize D-galactose in mixed carbon sources while retaining 3,6-anhydro L-galactose. This approach enables efficient, low-cost, and eco-friendly purification of 3,6-anhydro L-galactose, opening avenues for its widespread utilization.

Abiotic and Biotic Processes Controlling Deposition of Calcite and Hydrotalcite Calcretes on Niue Island, Southwest Pacific

Calcretes are indurated terrestrial carbonates that are widespread in arid and semi-arid settings and serve as important archives of present and past environments. Here, we use geochemical tools to explore the nature and origin of calcretes documented from tropical Niue Island in the Southwest Pacific. The study recognizes two types of calcretes that differ in their mineral assemblage, microfabrics, elemental chemistry, and carbon and oxygen isotopes. The calcretes common in the paleo-lagoon soils consist of 90% low-Mg calcite and ~10% highly weathered Mg-Al silicates. These pedogenic calcretes formed in the soil profiles within the vadose zone bear the following distinctions: (i) Fe/Al ratio of 0.75, identical to the ratio in soils (Fe/Al = 0.76 ± 0.5), substantiating the link between the calcretes and soils; (ii) presence of rhizoliths, root voids, micritic nodules, and clasts, which are consistent with a pedogenic calcrete fabric; and (iii) 13C and 18O depletions of −10.6‰ and −5.3‰, respectively, which are compatible with carbon sources from microbial and root respiration, as well as formation in oxygen isotope equilibrium with vadose waters. Unlike the pedogenic calcrete, a rare calcrete from the coastal terrace contains an exceptionally rare hydrotalcite [Mg6Al2(CO3)(OH)16(H2O)4] mineral (65%) coated by microbial films. We contend that the hydrotalcite-rich calcrete was deposited through interaction of dolomite with seawater, similar to the method of producing hydrotalcite in the laboratory. 13C and 18O enrichments of 0.8 to 1.7‰ and −1.0 to −1.6‰, respectively, are in agreement with (i) mixed carbon sources consisting of microbial CO2 degassing, seawater HCO3, and dolomite dissolution, and (ii) oxygen isotope equilibration with seawater-derived fluid.

Contribution of proton ATPase in the formation of the proton motive force during fermentation of mixed carbon sources

Contribution of proton ATPase in the formation of the proton motive force during fermentation of mixed carbon sources

Microbial co-cultivation: Reaction dynamics of combustible gases bioremediation in goaf

The accumulation of combustible gases in goaf is a key and difficult point in mine disaster prevention and control, which can easily lead to coal mine accidents and seriously safety production. Methanotrophs (S2, T7) and carboxydotrophic bacteria (M13) were extracted from mine environment to cocultivation. The cultivation conditions such as inoculation, temperature, and pH were selected to explore the effects of the growth and metabolic characteristics, and reveal the reaction kinetics of mixed strains (S2/M13, T7/M13). The results showed that the optimal inoculation amount for mixed strains was 5 %, and the maximum range of mixed carbon source inoculation for S2/M13 and T7/M13 were 9.69 % CH4+(7.27–9.69 % CO) and 9.69 % CH4+(4.35–7.27 % CO), the optimal cultivation temperatures were 25, 30 ℃, respectively, and the optimal pH was 7. In addition, the CH4 metabolic rates of S2/M13 and T7/M13 were 72.4 % and 85.4 %, respectively, and the CO metabolic rate reached over 95 % under the above optimal conditions, the processes of growth and metabolism of the mix cultures remained consistent. Moreover, the growth curves of the S2/M13 and T7/M13 conformed to the Logistic model, and whose attenuation coefficients (b) were 0.035, −0.215 d−1, the maximum specific growth rates (umax) were 0.524, 0.862 d−1, respectively. At the same time, the reaction rate of combustible gases showed high consistency in the logarithmic and stationary phases of the mixed strains, and exhibited a good linear relationship with the consumption rate of O2, the inhibitory kinetics of mixed strains on the reaction rate of combustible gases under different cultivation conditions were determined. The research results have vital theoretical and practical significance for the prevention and control of combustible gases and the safe mining in coal mines.

Ferulic acid triggering a co-production of 4-vinyl guaiacol and fumaric acid from lignocellulose-based carbon source by Rhizopus oryzae

Plant secondary metabolites have attracted considerable attention due to the increasing demand for finite fossil resources and environmental concerns. However, the biosynthesis of aromatic aldehydes or alcohols from renewable resources remains challenging and costly. This study explores a novel approach performed by the aromatic catabolizing organism Rhizopus oryzae, which enables a ferulic acid-activated co-production of 4-vinyl guaiacol (4-VG) and fumaric acid. The strain produced 4.60 g/L 4-VG and 11.25 g/L fumaric acid from a mixed carbon source of glucose and xylose, suggesting that this new pathway allows the potential production of natural 4-VG from low-cost substrates. This green route, which utilizes Rhizopus oryzae's ability to efficiently convert various renewable resources into valuable chemicals, paves the way for improved catalytic efficiency in 4-VG production.

Mechanism of A. oleivorans S4 treating soluble phosphorus deficiency and hydrocarbon contamination simultaneously

Both soluble phosphorus (P) deficiency and petroleum hydrocarbon contamination represent challenges in soil environments. While phosphate-solubilizing bacteria and hydrocarbon-degrading bacteria have been identified and employed in environmental bioremediation, the bacteria co-adapted to soluble P deficiency and hydrocarbon contamination has rarely been reported. This study explored the ability of Acinetobacter oleivorans S4 (A. oleivorans S4) to solubilize phosphate using n-hexadecane (H), glucose (G), and a mixed carbon source (HG) in tricalcium phosphate (TCP) medium. A. oleivorans S4 exhibited robust growth in H-TCP, releasing 31 mg L−1 of soluble P. Conversely, A. oleivorans S4 barely grew in G-TCP, releasing 654 mg L−1 of soluble P. In HG-TCP, biomass surpassed that in H-TCP, with phosphate release comparable to that in G-TCP. HPLC analysis revealed a small amount of TCA cycle acids in H-TCP and a large amount of gluconate in G-TCP and HG-TCP. Transcriptomic analysis showed elevated expression of genes associated with alkane degradation, P starvation, N utilization, and trehalose synthesis in H-TCP, revealing the molecular co-adaptation mechanism of A. oleivorans S4. Furthermore, the addition of glucose enhanced alkane degradation, P and N utilization, and reduced trehalose synthesis. It indicated that incomplete glucose metabolism may provide energy for other reactions, and the increase in soluble P mediated by gluconate may alleviate oxidative stress. Overall, A. oleivorans S4 proves promising for remediating soluble P-deficient and hydrocarbon-contaminated environments, and glucose stimulates its transformation into a super phosphate-solubilizing bacterium.

Feasibility study on heterotrophic utilization of galactose by Chlorella sorokiniana and promotion of galactose utilization through mixed carbon sources culture

BackgroundThe development of alternative carbon sources is important for reducing the cost of heterotrophic microalgae cultivation. Among cheap feedstocks, galactose is one of the most abundant sugars and can be easily obtained from many natural biomasses. However, it is generally difficult to be utilized by microalgae. In addition, the mechanism of its low utilization efficiency in heterotrophic cultivation is still unknown.ResultsAmong seven tested carbon sources, only glucose and acetate could be efficiently utilized by C. sorokiniana in heterotrophic cultivation while there were no apparent signs of utilization of other carbohydrates, including galactose, in regular heterotrophic cultivation. However, galactose could be utilized in cultures with high inoculation sizes. This confirmed that C. sorokiniana has a complete pathway for transporting and assimilating galactose under dark conditions, but the rate of galactose utilization is quite low. In addition, the galactose utilization was greatly enhanced in mixotrophic cultures, which indicated that galactose utilization could be enhanced by additional pathways that can enhance cell growth. Based on above results, a mixed carbon source culture strategy was proposed to improve the utilization rate of galactose, and a significant synergistic effect on cell growth was achieved in cultures using a mixture of galactose and acetate.ConclusionsThis study indicated that the galactose metabolism pathway may not be inherently deficient in Chlorophyta. However, its utilization rate was too low to be detected in regular heterotrophic cultivation. Mixed carbon source culture strategy was confirmed effective to improve the utilization rate of galactose. This study contributes to a deeper understanding of the utilization ability of difficultly utilized substrates in the heterotrophic cultivation of microalgae, which is of great significance for reducing the cost of heterotrophic cultivation of microalgae.

Machine Learning-Assisted Optimization of Mixed Carbon Source Compositions for High-Performance Denitrification.

Appropriate mixed carbon sources have great potential to enhance denitrification efficiency and reduce operational costs in municipal wastewater treatment plants (WWTPs). However, traditional methods struggle to efficiently select the optimal mixture due to the variety of compositions. Herein, we developed a machine learning-assisted high-throughput method enabling WWTPs to rapidly identify and optimize mixed carbon sources. Taking a local WWTP as an example, a mixed carbon source denitrification data set was established via a high-throughput method and employed to train a machine learning model. The composition of carbon sources and the types of inoculated sludge served as input variables. The XGBoost algorithm was employed to predict the total nitrogen removal rate and microbial growth, thereby aiding in the assessment of the denitrification potential. The predicted carbon sources exhibited an enhanced denitrification potential over single carbon sources in both kinetic experiments and long-term reactor operations. Model feature analysis shows that the cumulative effect and interaction among individual carbon sources in a mixture significantly enhance the overall denitrification potential. Metagenomic analysis reveals that the mixed carbon sources increased the diversity and complexity of denitrifying bacterial ecological networks in WWTPs. This work offers an efficient method for WWTPs to optimize mixed carbon source compositions and provides new insights into the mechanism behind enhanced denitrification under a supply of multiple carbon sources.

Proton conductance and regulation of proton/potassium fluxes in Escherichia coli FhlA-lacking cells during fermentation of mixed carbon sources

Escherichia coli uptake potassium ions with the coupling of proton efflux and energy utilization via proton FOF1-ATPase. In this study contribution of formate hydrogen lyase (FHL) complexes in the proton/potassium fluxes and the formation of proton conductance (CMH+) were investigated using fhlA mutant strain. The proton flux rate (JH+) decreased in fhlA by ∼ 25 % and ∼70 % during the utilization of glucose and glycerol, respectively, at 20 h suggesting H+ transport via or through FHL complexes. The decrease in JK+ in fhlA by ∼40 % proposed the interaction between FHL and Trk secondary transport system during mixed carbon fermentation. Moreover, the usage of N,N′-dicyclohexylcarbodiimide (DCCD) demonstrated the mediation of FOF1-ATPase in this interaction. CMH+ was 13.4 nmol min−1 mV−1 in WT at 20 h, which decreased by 20 % in fhlA. Taken together, FHL complexes have a significant contribution to the modulation of H+/K+ fluxes and the CMH + for efficient energy transduction and regulation of the proton motive force during mixed carbon sources fermentation.

KERATINOLYTIC POTENTIAL OF MICROMYCETE ASPERGILLUS CLAVATUS VKPM F-1593 AND COMPARISON OF ITS ENZYMES WITH THE COMMERCIAL KERATINASE PREPARATION

Animal husbandry is a rapidly developing branch of agriculture, increasing the volume of production annually, and keratin-containing waste (feathers, bristles) make up the majority of all waste from this industry. The development of methods of environmentally friendly processing of such waste to obtain valuable resources (amino acids and oligopeptides) is an important mission of modern science, including biotechnology. One of the ways to dispose of animal husbandry waste that meets modern trends in the development of a green economy is the use of microorganisms and their enzymes. The possibility of obtaining keratinolytic enzymes of Aspergillus clavatus VKPM F-1593 under deep conditions with various sources of nitrogen and carbon, including with the growth of the producer on animal waste, was studied. The highest target activity (96.1 E) was achieved using mixed carbon and nitrogen sources: inorganic - sodium nitrate, easily digestible organic - fi sh meal hydrolysate and hard-toreach organic - ground chicken feather. Varying the content of various substrates in the composition of fermentation media allowed not only to regulate the level of proteolytic activity, but also to reach the peak of producer activity on diff erent days of cultivation. The specifi c keratinase activity of A. clavatus VKPM F-1593 (pI 9.3) to various protein substrates with the activity of a commercial proteinase K. Both enzymes showed a similar level of activity regarding most of the substrates used. However, protease A. clavatus VKPM F-1593 has a greater overall proteolytic activity, which confi rms the prospects of this culture for biodegradation of animal waste

Exploratory study on the metabolic similarity of denitrifying carbon sources.

Mixed carbon sources have been developed for denitrification to eliminate the "carbon dependency" problem of single carbon. The metabolic correlation between different carbon sources is significant as guidance for the development of novel mixed carbon sources. In this study, to explore the metabolic similarity of denitrifying carbon sources, we selected alcohols (methanol, ethanol, and glycerol) and saccharide carbon sources (glucose, sucrose, and starch). Batch denitrification experiments revealed that methanol-acclimated sludge improved the denitrification rate of both methanol (14.42 mg-N/gMLVSS*h) and ethanol (9.65 mg-N/gMLVSS*h), whereas ethanol-acclimated sludge improved the denitrification rate of both methanol (7.80 mg-N/gMLVSS*h) and ethanol (22.23 mg-N/gMLVSS*h). In addition, the glucose-acclimated sludge and sucrose-acclimated sludge possibly improved the denitrification rate of glucose and sucrose, and the glycerol-acclimated sludge improved the denitrification rate of volatile fatty acids (VFAs), alcohols, and saccharide carbon sources. Functional gene analysis revealed that methanol, ethanol, and glycerol exhibited active alcohol oxidation and glyoxylate metabolism, and glycerol, glucose, and sucrose exhibited active glycolysis metabolism. This indicated that the similarity in the denitrification metabolism of these carbon sources was based on functional gene similarity, and glycerol-acclimated sludge exhibited the most diverse metabolism, which ensured its good denitrification effect with other carbon sources.

Regulation of metabolism and proton motive force generation during mixed carbon fermentation by an Escherichia coli strain lacking the FOF1-ATPase

Proton FOF1-ATPase is the key enzyme in E. coli under fermentative conditions. In this study the role of E. coli proton ATPase in the μ and formation of metabolic pathways during the fermentation of mixture of glucose, glycerol and formate using the DK8 (lacking FOF1) mutant strain was investigated. It was shown that the contribution of FOF1-ATPase in the specific growth rate was ∼45 %. Formate was not taken up in the DK8 strain during the initial hours of the growth. The utilization rates of glucose and glycerol were unchanged in DK8, however, the production of succinate, lactate and ethanol was decreased causing a reduction of the redox state up to −450 mV. Moreover, the contribution of FOF1-ATPase in the interplay between H+ and H2 cycles was described depending on the bacterial growth phase and main utilizing substrate. Besides, the H2 production rate in the DK8 strain was decreased by ∼60 % at 20 h and was absent at 72 h. Δp was decreased from −157 ± 4.8 mV to −140 ± 4.2 mV at 20 h and from −195 ± 5.9 mV to −148 ± 4.4 mV at 72 h, compared to WT. Taken together it can be concluded that during fermentation of mixed carbon sources metabolic cross talk between FOF1-ATPase-TrkA-Hyd-Fdh-H is taking place for maintaining the cell energy balance via regulation proton motive force.

High-Level Biosynthesis of Chlorogenic Acid from Mixed Carbon Sources of Xylose and Glucose through a Rationally Refactored Pathway Network.

Chlorogenic acid (CGA) has incredible potential for various pharmaceutical, nutraceutical, and agricultural applications. However, the traditional extraction approach from plants is time-consuming, further limiting its production. Herein, we design and construct the de novo biosynthesis pathway of CGA using modular coculture engineering in Escherichia coli, which is composed of MG09 and BD07 strains. To accomplish this, the phenylalanine-deficient MG09 strain was engineered to utilize xylose preferentially and to overproduce precursor caffeic acid, while the tyrosine-deficient BD07 strain was constructed to consume glucose exclusively to enhance another precursor quinic acid availability for the biosynthesis of CGA. Further pathway modularization and balancing in the context of syntrophic cocultures resulted in additional production improvement. The coculture strategy avoids metabolic flux competition in the biosynthesis of two CGA precursors, caffeic acid and quinic acid, and allows for production improvement by balancing module proportions. Finally, the optimized coculture based on the aforementioned efforts produced 131.31 ± 7.89 mg/L CGA. Overall, the modular coculture engineering strategy in this study provides a reference for constructing microbial cell factories that can efficiently biomanufacture complex natural products.

An optimized heating source for heat-not-burn tobacco products through synergistic combustion of tobacco stalk and graphite carbon with K2CO3 catalyst.

Waste tobacco stalk is blended with graphite carbon to form a composite carbon source, which is a promising external heating system for heat-not-burn tobaccos. In the current work, the effects of tobacco stalk amounts and the catalyst K2CO3 on the co-combustion characteristics (i.e., the ignition temperature, burnout temperature, etc.) of graphite carbon were investigated. As a result, the ignition temperatures of the blend were determined by the tobacco straw, while the burnout temperature of the samples was reduced by approximately 60 °C due to the addition of a tobacco stalk. After the addition of K2CO3, the ignition temperatures of the mixture were further decreased by 2-7 °C since the ignition temperature of the tobacco stalk was difficult to further reduce after K2CO3 addition. Meanwhile, the burnout temperature can be reduced by 76-106 °C because the presence of K2CO3 can significantly improve the combustion of graphite carbon. In addition, the kinetic analysis revealed that during the release of volatile matter, the oxidation process accords with the first-order kinetic model, while in the combustion process of mixed carbon source, the combustion process can be described by the third-order kinetic model.

Highly efficient production of rhamnolipid in P. putida using a novel sacB-based system and mixed carbon source

Pseudomonas putida KT2440, a GRAS strain, has been used for synthesizing bulk and fine chemicals. However, the gene editing tool to metabolically engineer KT2440 showed low efficiency. In this study, a novel sacB-based system pK51mobsacB was established to improve the efficiency for marker-free gene disruption. Then the rhamnolipid synthetic pathway was introduced in KT2440 and genes of the competitive pathways were deleted to lower the metabolic burden based on pK51mobsacB. A series of endogenous and synthetic promoters were used for fine tuning rhlAB expression. The limited supply of dTDP-L-rhamnose was enhanced by heterologous rmlBDAC expression. Cell growth and rhamnolipid production were well balanced by using glucose/glycerol as mixed carbon sources. The final strain produced 3.64 g/L at shake-flask and 19.77 g/L rhamnolipid in a 5 L fermenter, the highest obtained among metabolically engineered KT2440, which implied the potential of KT2440 as a promising microbial cell factory for industrial rhamnolipid production.

Enhanced biological phosphorus removal from wastewater and dynamics of microbial population in dual PAOs symbiosis system

Low level of volatile fatty acids (VFAs) is a key factor limiting the performance of enhanced biological phosphorus removal (EBPR) by traditional polyphosphate accumulating organisms (PAOs). A newly discovered PAOs capable of fermenting macromolecular organic matter into short-chain VFAs could solve the problem. However, the roles of traditional and fermented PAOs in wastewater treatment processes and the collaboration between functional microorganisms remain unknown. In this study, a sequencing batch reactor (SBR) was operated with alternating anaerobic oxic (An/O) mode to investigate the effect of mixed carbon source ratios, namely, acetate (NaAc):casein hydrolysate (Cas aa) = 4:0, 3:1, 1:1, 1:3 and 0:4, on EBPR performance and microbial community structure. The results showed that the phosphorus removal efficiency remained stable as NaAc was the sole carbon source. When NaAc:Cas aa varied from 3:1 to 1:3, the recovery of system performance took less time compared to the last Run, implying an adaptation of PAOs to Cas aa. Moreover, the anaerobic phosphorus release time was found to increase with the increasing amount of VFAs from Cas aa degradation, indicating the enrichment of fermented bacteria and the utilization of VFAs by traditional PAOs. Increasing the dose of Cas aa also generated more NH4+-N, owing to the reaction of the groups in the amino acids with water, causing a drastic decrease of ammonium removal efficiency from 88.9 % to 15.2 %. The ideal process performance implied that EBPR by dual PAOs synergistic symbiosis occurred in the system with NaAc:Cas aa = 1:1. Meanwhile, the results of 16S ribosomal RNA (16S rRNA) genes-Illumina MiSeq high-throughput sequencing showed that the abundance of traditional PAOs decreased from 22.4 % (4:0) to 11.6 % (1:1) and to 4.9 % (0:4), but fermented PAOs increased from 9.9 % to 19.5 %, then decreased to 17.3 %. Dual PAOs synergistic symbiosis could be of great potential for EBPR in treating low VFAs wastewater.

Metabolic engineering of Halomonas bluephagenesis for high-level mevalonate production from glucose and acetate mixture

Mevalonate (MVA) plays a crucial role as a building block for the biosynthesis of isoprenoids. In this study, we engineered Halomonas bluephagenesis to efficiently produce MVA. Firstly, by screening MVA synthetases from eight different species, the two efficient candidate modules, specifically NADPH-dependent mvaESEfa from Enterococcus faecalis and NADH-dependent mvaESLca from Lactobacillus casei, were integrated into the chromosome, leading to the construction of the H. bluephagenesis MVA11. Through the synergetic utilization of glucose and acetate as mixed carbon sources, MVA11 produced 11.2 g/L MVA with a yield of 0.45 g/g (glucose + acetic acid) in the shake flask. Subsequently, 10 beneficial genes out of 50 targets that could promote MVA production were identified using CRISPR interference. The simultaneous repression of rpoN (encoding RNA polymerase sigma-54 factor) and IldD (encoding L-lactate dehydrogenase) increased MVA titer (13.3 g/L) by 19.23% and yield (0.53 g/g (glucose + acetic acid)) by 17.78%, respectively. Furthermore, introducing the non-oxidative glycolysis (NOG) pathway into MVA11 enhanced MVA yield by 12.20%. Ultimately, by combining these strategies, the resultant H. bluephagenesis MVA13/pli-63 produced 13.9 g/L MVA in the shake flask, and the yield increased to 0.56 g/g (glucose + acetic acid), which was the highest reported so far. Under open fed-batch fermentation conditions, H. bluephagenesis MVA13/pli-63 produced 121 g/L of MVA with a yield of 0.42 g/g (glucose + acetic acid), representing the highest reported titer and yield in the bioreactor to date. This study demonstrates that H. bluephagenesis is one of the most favorable chassis for MVA production.

Multi-omics analyses reveal metabolic pathways of benzo[a]pyrene biodegradation under sole or mixed carbon sources

Proteomics and metabolomics can be used to efficiently and conveniently assess proteins and metabolites during microbial degradation of pollutants; these analytical techniques are closely correlated and mutually confirmed and provide a means to explore degradation pathways. The degradation pathways and regulatory characteristics of Microbacterium sp. M. CSW3 for the metabolism of benzopyrene (BaP) alone and in the presence of phenanthrene and pyrene were investigated using these omics. Proteomics results showed that CLP protease, ABC transporter, aldehyde dehydrogenase, and enoyl-CoA hydratase were important for the metabolism of polycyclic aromatic hydrocarbons (PAHs). Five pathways for the microbial degradation of benzopyrene were suggested by metabolomics, and phenanthrene was identified as an intermediate metabolite. Further, correlation analysis showed that the two stress environments inhibited the biosynthesis of bacterial amino acids. The glycolysis/gluconeogenesis and fatty acid degradation pathways played a positive role in energy acquisition and PAHs degradation. Addition of low-molecular-weight PAHs promoted the production of related enzyme systems and also made the degradation of BaP more thorough. This study provides efficient concepts and methods for the exploration of degradation mechanisms of high-molecular-weight PAHs and co-metabolism of mixed PAHs.