Suitable Carbon Source Research Articles

Metagenomic insights into the microbial cooperative networks of a benz(a)anthracene-7,12-dione degrading community from a creosote-contaminated soil

Genotoxicity of PAH-contaminated soils can eventually increase after bioremediation due to the formation and accumulation of polar transformation products, mainly oxygenated PAHs (oxy-PAHs). Biodegradation of oxy-PAHs has been described in soils, but information on the microorganisms and mechanisms involved is still scarce. Benz(a)anthracene-7,12-dione (BaAQ), a transformation product from benz(a)anthracene frequently detected in soils, presents higher genotoxic potential than its parent PAH. Here, using sand-in-liquid microcosms we identified a specialized BaAQ-degrading subpopulation in a PAH-contaminated soil. A BaAQ-degrading microbial consortium was obtained by enrichment in sand-in-liquid cultures with BaAQ as sole carbon source, and its metagenomic analysis identified members of Sphingobium, Stenotrophomonas, Pusillimonas, Olivibacter, Pseudomonas, Achromobacter, and Hyphomicrobiales as major components. The integration of data from metabolomic and metagenomic functional gene analyses of the consortium revealed that the BaAQ metabolic pathway was initiated by Baeyer-Villiger monooxygenases (BVMOs). The presence of plasmid pANTQ-1 in the metagenomic sequences, identified in a previous multi-omic characterization of a 9,10-anthraquinone-degrading isolate recovered from the same soil, suggested the occurrence of a horizontal gene transfer event. Further metagenomic analysis of the BaAQ-degrading consortium also provided insights into the potential roles and interactions within the consortium members. Several potential auxotrophies were detected, indicating that relevant nutritional interdependencies and syntrophic associations were taking place within the community members, not only to provide suitable carbon and energy sources, but also to supply essential nutrients and cofactors. Our work confirms the essential role that BVMO may play as a detoxification mechanism to mitigate the risk posed by oxy-PAH formation during bioremediation of contaminated soils.

Genomic Characteristics and Comparative Genomics Analysis of the Endophytic Fungus Paraphoma chrysanthemicola DS-84 Isolated from Codonopsis pilosula Root.

Paraphoma chrysanthemicola is a newly identified endophytic fungus. The focus of most studies on P. chrysanthemicola has been on its isolation, identification and effects on plants. However, the limited genomic information is a barrier to further research. Therefore, in addition to studying the morphological and physiological characteristics of P. chrysanthemicola, we sequenced its genome and compared it with that of Paraphoma sp. The results showed that sucrose, peptone and calcium phosphate were suitable sources of carbon, nitrogen and phosphorus for this strain. The activities of amylase, cellulase, chitosanase, lipase and alkaline protease were also detected. Sequencing analysis revealed that the genome of P. chrysanthemicola was 44.1 Mb, with a scaffold N50 of 36.1 Mb and 37,077 protein-coding genes. Gene Ontology (GO) annotation showed that mannose-modified glycosylation was predominant in monosaccharide utilisation. The percentage of glycoside hydrolase (GH) modules was the highest in the carbohydrate-active enzymes database (CAZy) analysis. Secondary metabolite-associated gene cluster analysis identified melanin, dimethylcoprogen and phyllostictine A biosynthetic gene clusters (>60% similarity). The results indicated that P. chrysanthemicola had a mannose preference in monosaccharide utilisation and that melanin, dimethylcoprogen and phyllostictine A were important secondary metabolites for P. chrysanthemicola as an endophytic fungus.

Mechanical and ablation properties of Cf/SiBCN-ZrB2 composites prepared by an in-situ reaction: Effect of carbon source

SiBCN ceramics were prepared by a novel inorganic method: the in situ reaction of amorphous SiBON and C. Differences in the mechanical and ablation properties of composites prepared from flake graphite and carbon black (denoted as Cf/CGZ and Cf/CBZ, respectively) were compared to find a suitable carbon source. The results showed that flake graphite is the optimal carbon source. The fracture toughness of the Cf/CGZ composite was 9.1 ± 0.4 MPa·m1/2, which is 23.0% higher than that of the Cf/CBZ composite. This is because the flake graphite promoted crack deflection. Furthermore, after exposure to a plasma flame with a heat flux of 6.68 MW/m2 for 300 s, the mass and linear ablation rates of the Cf/CGZ composite are 0.39 mg/s and − 0.19 µm/s, respectively, which is a decrease of 22.00% and 64.81%, respectively, as compared to those of the Cf/CBZ composite. This is because of the directional distribution of flake graphite, which improved the thermal conductivity, reduced the ablation surface temperature, and facilitated the formation of a dense ZrO2/SiO2 layer as an anti-ablation barrier.

Dextranase Production Using Marine Microbacterium sp. XD05 and Its Application.

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0-8.0). The addition of NH4+ increased dextranase activity, while Co2+ and Mn2+ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture.

Impact of Fermentation Conditions and Purification Strategy on Bacterial Cellulose Properties

Bacterial cellulose (BC) has attracted much research interest, delivering a combination of exclusive properties, such as flexibility, hydrophilicity, crystallinity and a three-dimensional network. In this study, the effects of carbon source and cultivation conditions on BC production by the bacterium Acetobacter xylinum subsp. sucrofermentans DSM 15973 were assessed. Fructose was the most suitable carbon source and high BC concentrations up to 31 g l–1 were achieved in substrates with 60 g l–1 fructose under static culture conditions. Notably, BC production was equally high under the same fermentation conditions in agitated cultures (~30 g l–1). Moreover, the effectiveness of sodium hydroxide and sodium hypochlorite solutions in BC purification and their potential impact on BC structure and properties were explored. The combination of weak NaOH and NaOCl proved an effective purification method, preserving the fibre structure and crystallinity of BC.

Meta-analysis of transcriptome reveals key genes relating to oil quality in olive

BackgroundOlive oil contains monounsaturated oleic acid up to 83% and phenolic compounds, making it an excellent source of fat. Due to its economic importance, the quantity and quality of olive oil should be improved in parallel with international standards. In this study, we analyzed the raw RNA-seq data with a meta-analysis approach to identify important genes and their metabolic pathways involved in olive oil quality.ResultsA deep search of RNA-seq published data shed light on thirty-nine experiments associated with the olive transcriptome, four of these proved to be ideal for meta-analysis. Meta-analysis confirmed the genes identified in previous studies and released new genes, which were not identified before. According to the IDR index, the meta-analysis had good power to identify new differentially expressed genes. The key genes were investigated in the metabolic pathways and were grouped into four classes based on the biosynthetic cycle of fatty acids and factors that affect oil quality. Galactose metabolism, glycolysis pathway, pyruvate metabolism, fatty acid biosynthesis, glycerolipid metabolism, and terpenoid backbone biosynthesis were the main pathways in olive oil quality. In galactose metabolism, raffinose is a suitable source of carbon along with other available sources for carbon in fruit development. The results showed that the biosynthesis of acetyl-CoA in glycolysis and pyruvate metabolism is a stable pathway to begin the biosynthesis of fatty acids. Key genes in oleic acid production as an indicator of oil quality and critical genes that played an important role in production of triacylglycerols were identified in different developmental stages. In the minor compound, the terpenoid backbone biosynthesis was investigated and important enzymes were identified as an interconnected network that produces important precursors for the synthesis of a monoterpene, diterpene, triterpene, tetraterpene, and sesquiterpene biosynthesis.ConclusionsThe results of the current investigation can produce functional data related to the quality of olive oil and would be a useful step in reducing the time of cultivar screening by developing gene specific markers in olive breeding programs, releasing also new genes that could be applied in the genome editing approach.

ZSM-5 Templated Porous Carbon: Synthesis and Characterization

Microporous zeolite ZSM-5 is prepared by the hydrothermal method, and its structure is tuned by changing the hydrothermal conditions. Then zeolite particles with uniform size and dispersion are etched into the hollow porous structures with an alkali solution to form zeolite templates. Porous carbon materials with ordered pore channels are acquired by the carbon deposition method (CVD). The detailed steps include introducing suitable carbon sources into the pore channels of the as-prepared zeolite templates, followed by carbon vapor deposition and continuous optimization of the deposition conditions, and finally, removing the template. The hollow porous structure of the carbon material facilitates the exposure of catalytic active sites and the improvement of diffusion kinetics. The hollow porous carbon (HPC) formed by carbon deposition perfectly inherits the structure and pore attributes of the hollow hierarchical zeolite ZSM-5. It can be further used as a carbon-based catalyst support.

Development of a Strategy for L-Lactic Acid Production by Rhizopus oryzae Using Zizania latifolia Waste and Cane Molasses as Carbon Sources.

As a biodegradable and renewable material, polylactic acid is considered a major environmentally friendly alternative to petrochemical plastics. Microbial fermentation is the traditional method for lactic acid production, but it is still too expensive to compete with the petrochemical industry. Agro-industrial wastes are generated from the food and agricultural industries and agricultural practices. The utilization of agro-industrial wastes is an important way to reduce costs, save energy and achieve sustainable development. The present study aimed to develop a method for the valorization of Zizania latifolia waste and cane molasses as carbon sources for L-lactic acid fermentation using Rhizopus oryzae LA-UN-1. The results showed that xylose derived from the acid hydrolysis of Z. latifolia waste was beneficial for cell growth, while glucose from the acid hydrolysis of Z. latifolia waste and mixed sugars (glucose and fructose) from the acid hydrolysis of cane molasses were suitable for the accumulation of lactic acid. Thus, a three-stage carbon source utilization strategy was developed, which markedly improved lactic acid production and productivity, respectively reaching 129.47 g/L and 1.51 g/L·h after 86 h of fermentation. This work demonstrates that inexpensive Z. latifolia waste and cane molasses can be suitable carbon sources for lactic acid production, offering an efficient utilization strategy for agro-industrial wastes.

Influence of Different Types of Carbon Sources on Glucosinolate and Phenolic Compounds in Radish Sprouts

Radish sprouts are valued as a key nutrient-dense food in Asian countries. In the current study, we examined how radish sprouts responded to treatments with various carbon sources. The influence of those treatments in parameters such as plant growth and glucosinolate and phenolic compounds levels were analyzed. A positive correlation between plant growth and the accumulation of glucosinolates and phenolics was observed. In this study, except for galactose treatment, all other carbon-exposed radish sprouts showed the highest shoot and root length and fresh weight. Seven different glucosinolate and five phenolic compounds were identified in radish sprouts. The total glucosinolates and phenolic compound content were increased after treatments with different carbon sources. Radish sprouts exposed to sucrose showed the highest total glucosinolates and phenolics content, which was 1.22-fold and 1.45-fold higher than that of untreated sprouts, respectively. Moreover, sucrose exposure led to a higher production of glucoiberin, gluconapoleiferin, 4-hydroxyglucobrassicin, glucoerucin, glucoraphasatin, glucobrassicin, gallic acid, sinapic acid, rutin, and p-coumaric acid compared to that of untreated sprouts. The results obtained in this study will be helpful for researchers around the world to enhance specific glucosinolate and phenolic compounds by treating the radish sprout plants with suitable carbon sources.

Linking nitrate removal, carbon cycling, and mobilization of geogenic trace metals during infiltration for managed recharge

We present results from a series of laboratory column studies investigating the impacts of infiltration dynamics and the addition of a soil-carbon amendment (wood mulch or almond shells) on water quality during infiltration for flood-managed aquifer recharge (flood-MAR). Recent studies suggest that nitrate removal could be enhanced during infiltration for MAR through the application of a wood chip permeable reactive barrier (PRB). However, less is understood about how other readily available carbon sources, such as almond shells, could be used as a PRB material, and how carbon amendments could impact other solutes, such as trace metals. Here we show that the presence of a carbon amendment increases nitrate removal relative to native soil, and that there is greater nitrate removal in association with longer fluid retention times (slower infiltration rates). Almond shells promoted more efficient nitrate removal than wood mulch or native soil, but also promoted the mobilization of geogenic trace metals (Mn, Fe, and As) during experiments. Almond shells in a PRB likely enhanced nitrate removal and trace metal cycling by releasing labile carbon, promoting reducing conditions, and providing habitat for microbial communities, the composition of which shifted in response. These results suggest that limiting the amount of bioavailable carbon released by a carbon-rich PRB may be preferred where geogenic trace metals are common in soils. Given the dual threats to groundwater supplies and quality worldwide, incorporating a suitable carbon source into the soil for managed infiltration projects could help to generate co-benefits and avoid undesirable results.

Cytochrome P450-mediated co-metabolism of fluoroquinolones by Haematococcus lacustris for simultaneously promoting astaxanthin and lipid accumulation

Microalgae-based antibiotic removal treatment has attracted attention because of its low carbon and sustainable advantages. The microalgal co-metabolism system with a suitable carbon source leads to enhanced performance of pollutant removal. However, currently, limited knowledge is available for the removal of fluoroquinolone using a microalgae-mediated co-metabolism system. In this study, we first investigated that the biotic processes by alga Haematococcus lacustris in the co-metabolism system by adding glycerol would be the main contributors responsible for the removal of 10 mg/L ofloxacin (OFL) with the efficiency of 79.73% and the removal of 10 mg/L enrofloxacin (ENR) with the efficiency of 54.10%, respectively. Furthermore, we found that pyruvate from glycerol was converted into substrates and precursors, thereby resulting in the significant accumulations of microalgal astaxanthin and lipid. The astaxanthin content of H. lacustris was achieved at 4.81% and 4.69% treated with OFL and ENR in the presence of glycerol, with 16.04% and 14.55% of lipid content, respectively. The proposed metabolites and pathways were identified to plausibly explain the biodegradation of fluoroquinolone by H. lacustris. The molecular analyses demonstrated that cytochrome P450 (CYP450) enzymes are responsible for the biodegradation of fluoroquinolone, and it was further verified that fluoroquinolones might insert into CYP450 to finally form an efficient and tight binding conformation by molecular dynamic simulation. These findings provide a microalgae-based route for feasible and sustainable biodegradation of antibiotics using a co-metabolism strategy comprising glycerol as a carbon source, with the synergistic accumulation of valuable products.

Analysis of the structure and function of microbial community in late-stage of grass carp (Ctenopharyngodon idella) farming ponds

Microbial communities in aquaculture ponds play a critical role in pond productivity and the success of fish production. Nevertheless, our current understanding of the functional diversity of bacterial microbiomes in grass carp pond water and sediments is fragmentary. This study utilized high-throughput sequencing technology and community level physiological profiling (CLPP) methods to investigate microbial communities and metabolic activity of bacterial found in water samples and sediments from eight typical grass carp (Ctenopharyngodon idella) culturing pond in southern China. The correlations between putative function using PICRUSt2 and actual metabolic profiles via Biolog EcoPlates was assessed. Carbohydrates (32.51 %), amino acids (23.13 %), and polymers (16.61 %) were the most dominant carbon sources utilized by the microbial community in the sediment; while carbohydrates (34.72 %), amino acids (25.49 %), and polymers (16.15 %) were also utilized most often in the water samples. In the sediment samples, Proteobacteria (24.67 %), Chloroflexi (15.30 %), and Firmicutes (13.74 %) were the most dominant bacteria phyla. Actinobacteriota (32.62 %), Cyanobacteria (25.06 %), and Proteobacteria (17.51 %) were the most dominant bacteria phyla in the water samples. Moreover, our results suggested that the nitrogen transformations bacterial genera (Bacillus, Bradyrhizobium, Brocadia, Halomonas, and Vogesella) were positively correlated with carbon source utilization of the microbial community in the Biolog EcoPlates in the sediment. Dechloromonas and Pseudomonas were significantly negatively correlated in the water samples. In addition, there was a significant correlation between predicted function and the actual metabolic characteristics of microbial communities in sediment and water samples. The results facilitate detailed perspective of the relationship between the microbial community structure and the function in grass carp ponds and also provide a reference for the selection of suitable carbon sources in aquaculture wastewater treatment technology.

From Dinitrogen to N-Containing Organic Compounds: Using Li2CN2 as a Synthon.

By synergizing the heterogeneous synthetic approach with the homogeneous synthetic methodology, N-containing organic compounds can be synthesized via activated N-containing species prepared from N2 gas and suitable carbon sources. From N2, carbon, and LiH, we have previously succeeded in the high-yield preparation of Li2CN2 as the activated N-containing species. In this work, we applied Li2CN2 as a novel synthetic synthon for constructing N-containing organic compounds. A series of reaction models, including substitution reaction, cycloaddition reaction, and transition metal-catalyzed coupling reaction, were successfully performed using Li2CN2 under mild conditions. Various valuable cyanamides, carbodiimides, N-aryl cyanamides and 1,2,4-triazole derivatives were readily synthesized in moderate to excellent yields. With this method, the 15N-labeled products, including oxazolidine derivatives with anti-cancer activity, could also be facilely prepared from 15N2 gas.

From Dinitrogen to N‐Containing Organic Compounds: Using Li2CN2 as a Synthon

AbstractThrough the synergies of a heterogeneous synthetic approach and a homogeneous synthetic methodology, N‐containing organic compounds can be synthesized via activated N‐containing species prepared from N2 gas and suitable carbon sources. From N2, carbon, and LiH, we have previously succeeded in the high‐yield preparation of Li2CN2 as the activated N‐containing species. In this work, we applied Li2CN2 as a novel synthetic synthon for constructing N‐containing organic compounds. A series of reaction models, including a substitution reaction, cycloaddition reaction, and transition metal‐catalyzed coupling reaction, were successfully performed using Li2CN2 under mild conditions. Various valuable cyanamides, carbodiimides, N‐aryl cyanamides and 1,2,4‐triazole derivatives were readily synthesized in moderate to excellent yields. With this method, the 15N‐labeled products, including oxazolidine derivatives with anti‐cancer activity, could also be facilely prepared from 15N2 gas.

Effects of organic carbon sources on algal biofilm formation and insight into mechanism

Algal biofilm cultivation has great potential in producing high biomass yields and reducing harvesting costs. Organic carbon sources can promote algal growth in suspended cultivation, but their effects on algal biofilm formation and related mechanism have rarely been studied. In this study, we determined the most suitable organic carbon source and its concentration for the formation of algal biofilm, and structure/composition characteristics of extracellular polymeric substances (EPS) from algal biofilm. The results showed that the glycerol concentration of 1000 mg C L−1 in algal biofilm system was the most suitable condition to contribute to the biofilm formation and enhance attached biomass among the treatments. The algal biofilm at the glycerol concentration excreted the contents of relatively high EPS and its protein (EPS-PN), which were beneficial to forming the biofilm. The high EPS-PN content was mainly attributed to the increased hydrophobic proline and alanine contents but declined hydrophilic glutamic acid for improving algal biofilm formation. These findings enhanced our understanding of the formation mechanism of algal biofilm under the organic carbon source condition and provided the theoretical basis for algal biofilm formation.

Enhanced Production of Lipstatin Through NTG Treatment of Streptomyces toxytricini KD18 at 5 L Bioreactor Level.

Lipstatin, natural inhibitor of pancreatic lipase produced by Streptomyces toxytricini and used as an anti-obesity drug. Chemical mutagenesis was performed with different concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (NTG) for strain improvement to obtain high yield of lipstatin. It was observed that the potential of the wild type strain to produce lipstatin (1.09 g/L) was very low. Selected mutants produced lipstatin in the range of 1.20-2.23 g/L at the flask level where maximum amount of lipstatin was produced by M5 mutant. For comparative study, both the parent and M5 mutant strain of S. toxytricini were grown at the lab scale bioreactor with suitable sources of carbon and nitrogen. Significant increase in the production of lipstatin was observed at the bioreactor level where the wild type strain produced 2.4 g/L of lipstatin, while through the NTG mutation, the production of lipstatin was 5.35 g/L. However, Dry Cell Weight (DCW) of the mutant strain was less in comparison with wild type strain and significant morphological differences were observed. Nearly 5 times increase in the production of lipstatin was achieved through NTG mutation and bioreactor-controlled conditions. It was determined that the NTG treatment might be beneficial for strain improvement to get a better candidate for lipstatin production on commercial scale.

Effects of Some Nutritional Factors on the Growth of Chlorella vulgaris in a Mixotrophic Cultivation

The microalgae Chlorella vulgaris is not only known as a source of lipid compounds for the biofuel industry but also as a potential source of biomass production for aquaculture. This study investigated the influence of some nutritional factors (organic carbon source and C:N ratio) on the growth rate of Chlorella vulgaris. Glucose, sodium acetate, and sucrose were used to check the effect of the carbon sources. Meanwhile, five different ratios of C:N (1:1, 6:1, 12:1, 18:1, and 24:1) were tested. Results showed that glucose was the most suitable source of organic carbon for the biomass development of the Chlorella vulgaris; the ratio C:N=18:1 equivalent to 52.92 mmol/L carbon and 2.94 mmol/L nitrogen is the most appropriate ratio to promote biomass increase. The maximum growth rate of C. vulgaris recorded in this study was 0.58±0.03 day-1 in treatment supplemented with glucose at ratio C:N=18:1.

Optimization of Xanthan Gum Production by Demerara Sugar Using Response Surface Methodology

Xanthan gum (XG) production using three Xanthomonas sp. strains (290, 472, and S6) was evaluated by applying a 23 full factorial central composite design response to study the interactive effects of the fermentation medium component concentrations as parameters to determine the efficiency of the gum production in batch experiments. The experimental variables were the carbon source (demerara sugar or sucrose), potassium phosphate dibasic, and magnesium sulfate. Experimental results showed the K2HPO4 concentration as the important parameter for XG production by using Xanthomonas axonopodis pv. manihotis IBSBF 290 and X. campestris pv. campestris IBSBF 472, while for the Xanthomonas sp. S6 strain, the MgSO4∙7H2O concentration was the determining factor in XG production using demerara sugar or sucrose as a carbon source. The strains of Xanthomonas 472 and S6, using demerara sugar and higher concentrations of salts, exhibited a higher yield of XG (36 and 32%) than when using sucrose and the same concentration of salts. The experimental outcomes highlighted demerara sugar as a suitable and efficient alternative carbon and micronutrient source for XG production. Despite the bacterial strain influence, the medium composition is crucial for this fermentation process. Therefore, the evaluated salts are important factors for XG production, and the demerara sugar can partially replace this mineral salt requirement as indicated by the face-centered composite experimental design due to its chemical composition. Overall, demerara sugar provides promising properties for XG production.

Metabolic engineering of Corynebacterium glutamicum for acetate-based itaconic acid production

BackgroundItaconic acid is a promising platform chemical for a bio-based polymer industry. Today, itaconic acid is biotechnologically produced with Aspergillus terreus at industrial scale from sugars. The production of fuels but also of chemicals from food substrates is a dilemma since future processes should rely on carbon sources which do not compete for food or feed. Therefore, the production of chemicals from alternative substrates such as acetate is desirable to develop novel value chains in the bioeconomy.ResultsIn this study, Corynebacterium glutamicum ATCC 13032 was engineered to efficiently produce itaconic acid from the non-food substrate acetate. Therefore, we rewired the central carbon and nitrogen metabolism by inactivating the transcriptional regulator RamB, reducing the activity of isocitrate dehydrogenase, deletion of the gdh gene encoding glutamate dehydrogenase and overexpression of cis-aconitate decarboxylase (CAD) from A. terreus optimized for expression in C. glutamicum. The final strain C. glutamicum ΔramB Δgdh IDHR453C (pEKEx2-malEcadopt) produced 3.43 ± 0.59 g itaconic acid L−1 with a product yield of 81 ± 9 mmol mol−1 during small-scale cultivations in nitrogen-limited minimal medium containing acetate as sole carbon and energy source. Lowering the cultivation temperature from 30 °C to 25 °C improved CAD activity and further increased the titer and product yield to 5.01 ± 0.67 g L−1 and 116 ± 15 mmol mol−1, respectively. The latter corresponds to 35% of the theoretical maximum and so far represents the highest product yield for acetate-based itaconic acid production. Further, the optimized strain C. glutamicum ΔramB Δgdh IDHR453C (pEKEx2-malEcadopt), produced 3.38 ± 0.28 g itaconic acid L−1 at 25 °C from an acetate-containing aqueous side-stream of fast pyrolysis.ConclusionAs shown in this study, acetate represents a suitable non-food carbon source for itaconic acid production with C. glutamicum. Tailoring the central carbon and nitrogen metabolism enabled the efficient production of itaconic acid from acetate and therefore this study offers useful design principles to genetically engineer C. glutamicum for other products from acetate.

A real time integrated approach for the treatment of petroleum industry oily waste through ancillary carbon metabolism and biocatalytic cascade induction

Recalcitrant hydrocarbons contamination by petroleum oil sludge (POS) disposal from the petroleum refining industry is a major environmental issue. Insufficient biomolecules (biosurfactant and degradative enzymes) production and passive metabolic transformation lead to more prolonged and incomplete bioremediation process. Herein, integration of ancillary carbon metabolism and biocatalytic cascade induction facilitated faster microbial growth, increased supply of precursors for macromolecule production and activated enzymatic degradation cascade. The agricultural by-product, rice husk found to be the suitable ancillary carbon source and elemental analysis of Carbon, Hydrogen and Nitrogen (CHN), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy analyses confirmed the microbial assimilation of the co-substrate. Divalent metal cations such as Cu2+, Fe2+ and Zn2+ were screened as essential enzyme activators, thereby induce the enzymatic degradation of POS. The integrative system exhibited the maximum aliphatic and aromatic hydrocarbons degradation of 96% and 92% during semi-pilot scale treatment (1 Kg of POS). Further, the functional annotation of the genome using Carbohydrate-active enzymes (CAZymes) provided specific insight into the genomic potential of E.xiangfangensis STP-3 in the concomitant metabolism of complex carbohydrates towards the enhanced enzymatic degradation of POS. These findings demonstrated that integrating ancillary metabolism and biomolecular machinery induction provides a sustainable POS clean-up strategy.