Microbial Production Of Organic Acids Research Articles

Promotion of rice seedlings growth and enhancement of cadmium immobilization under cadmium stress with two types of organic fertilizer

Cadmium (Cd)-contaminated soil poses a severe threat to crop production and human health, while also resulting in a waste of land resources. In this study, two types of organic fertilizer (ZCK: Low-content available iron; Z2: High-content available iron) were applied to Cd-contaminated soil for rice cultivation, and the effects of the fertilizer on rice growth and Cd passivation were investigated in conjunction with soil microbial analysis. Results showed that Z2 could alter the composition, structure, and diversity of microbial communities, as well as enhance the complexity and stability of the microbial network. Both 2% and 5% Z2 significantly increased the fresh weight and dry weight of rice plants while suppressing Cd absorption. The 2% Z2 exhibited the best Cd passivation effect. Gene predictions suggested that Z2 may promote plant growth by regulating microbial production of organic acids that dissolve phosphorus and potassium. Furthermore, it is suggested that Z2 may facilitate the absorption and immobilization of soil cadmium through the regulation of microbial cadmium efflux and uptake systems, as well as via the secretion of extracellular polysaccharides. In summary, Z2 can promote rice growth, suppress Cd absorption by rice, and passivate soil Cd by regulating soil microbial communities.

Organic acids production from lactic acid bacteria: A preservation approach

The lactic acid bacteria (LAB) are a group of gram-positive bacteria capable of converting carbohydrate substrates into organic acids and producing a wide range of metabolites. Organic acids, including propionic, formic, acetic acid, and lactic acid, create an unfavorable environment for the growth of spoilage and pathogenic microorganisms. Also, they are employed as monomers or starting ingredients for food-based supplements, biomaterials, and biodegradable polymers. Organic acids from LAB have the potential to prevent spoilage and improve food taste that enhances consumer acceptance and appeal. Organic acids can be useful as starting materials in multiple applications, including food, chemical, cosmetic, pharmaceutical, and beverage industries owing to their various functional properties. Additionally, the use of LAB for organic acids production can replace petroleum-based processes due to their ability to utilize inexpensive and renewable feedstocks. This article aims to provide the potential of LAB as a biological catalyst for producing different organic acids. Also, the current review will give a critical snapshot of the strategies to improve microbial organic acid production and potential application of organic acids and discuss new challenges and opportunities for developing novel economically effective and sustainable nutritional sources and techniques.

Current advances in organic acid production from organic wastes by using microbial co‐cultivation systems

AbstractThe microbial production of organic acids has become a rapidly developing field due to their increasing global market. Recently, research has transitioned towards employing synthetic microbial consortia for organic acid production. Compared with pure cultures, microbial co‐cultures can perform more complex functions and endure more changeable environments. Accordingly, microbial co‐cultivation technologies for organic acid production have been adopted to fulfill the requirements for the utilization of a wider range of substrates for a higher product yield. Here, we have summarized current advances towards organic acid production from different substrates by using microbial co‐cultivation technologies. Furthermore, the construction mechanism of the microbial co‐cultivation systems was also analyzed and compared. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Enhancement of pyruvic acid production in Candida glabrata by engineering hypoxia-inducible factor 1

Dissolved oxygen (DO) supply plays essential roles in microbial organic acid production. Candida glabrata, as a dominant strain for producing pyruvic acid, principally converts glucose to pyruvic acid through glycolysis. However, this process relies excessively on high extracellular DO content. In this study, in combination with specific motif analysis of gene promoters, hypoxia-inducible factor 1 (HIF1) was engineered to improve the transcription level of some enzymes related to pyruvic acid synthesis under low DO level and directly led to increased pyruvic acid production and glycolysis efficiency. Moreover, the intracellular stability of HIF1 was further optimized from different aspects to maximize pyruvic acid accumulation. Finally, the pyruvic acid titer in a 5-L batch bioreactor with 10% DO level reached 53.1 g/L. As pyruvic acid is involved in the biosynthesis of various products, these findings suggest that HIF1-enabled regulation method has significant potential for increasing the synthesis of other chemicals in microorganisms.

Decrease of citric acid produced by Aspergillus niger through disruption of the gene encoding a putative mitochondrial citrate-oxoglutarate shuttle protein.

The transporter that exports citric acid (CA) generated in mitochondria to the cytosol is an important component of the CA production machinery of Aspergillus niger. In this report, we cloned and identified the gene cocA, encoding a 33.7-kDa putative mitochondrial citrate-oxoglutarate shuttle protein of the CA hyper-producer A. niger WU-2223L. The amount of CA produced by a representative cocA disruptant (35g/L) was significantly lower than that produced by strain WU-2223L (63g/L) after culture for 12days under CA production conditions, and the phenotype of the cocA disruptant differed in part from that of strain WU-2223L. A cocA disruptant complemented with cocA exhibited the same phenotypes as those of strain WU-2223L. This report is the first to show that cocA and its protein product clearly contribute to substantial CA production by A. niger, and provides a significant insight into microbial organic acid production by fermentation. Abbreviations: CA: citric acid; CD medium: Czapek-Dox medium; CS: citrate synthase; CTP: citrate transport protein; HR: homologous recombination; MCF: mitochondrial carrier family; RT-PCR: reverse-transcription PCR; TCA: tricarboxylic acid.

Isolation, occurrence, screening and characterization of rock phosphate solubilizing microbes

The present experiment is conducted on ‘isolation, Occurrence, Screening & Characterization of Rock phosphate solubilizing Microbes’. Phosphorus is the least mobile element in plant and soil contrary to other macronutrients. It precipitates in soil as orthophosphate or is absorbed by Fe and Al oxides through legend exchange. Phosphorus solubilizing bacteria play role in phosphorus nutrition by enhancing its availability to plants through release from inorganic and organic soil P pools by solubilization and mineralization Rock Phosphate is the cheapest and abundant Phosphatic fertilizer available but due to its sparse solubility. Most agricultural soils contain large reserves of phosphorus (P), a considerable part of which accumulates as a consequence of regular applications of P fertilizers. However, a greater part of soil phosphorus, approximately 95–99% is present in the form of insoluble phosphates and hence cannot be utilized by the plants combined application of rock phosphate with phosphate solubilizing microorganisms has emerged as a logical solution to this issue. The selection of microorganisms capable of solubilizing phosphorus (P) from rock phosphates (RP) may contribute to reduce the dependence of imported fertilizers in grain crops, reducing the costs of agricultural production, and also the environmental impacts. Principal mechanism in soil for mineral phosphate solubilization is lowering of soil pH by microbial production of organic acids and mineralization of organic P by acid phosphatase. Use of phosphorus solubilizing bacteria as inoculants increases P uptake. These bacteria also increase prospects of using phosphatic rocks in crop production. Greater efficiency of P solubilizing bacteria has been shown through co-inoculation with other beneficial bacteria and mycorrhiza In the present study bacterial and fungal strains were isolated from waste water, soil and sediment sample of ETP of Paradeep phosphate limited (PPL) and from Mahanadi river estuary (Paradeep), having potential to solubilize insoluble inorganic phosphates were characterized. Each isolates were tested for their tricalcium phosphate (TCP) and low grade rock phosphate (RP) solubilization efficiency in both solid and liquid medium. From the experiment it is found that out of 22 fungal isolates more than 50% were classified as efficient. There were significant differences in the availability of P among strains. From the Experiment it is also revealed that the solubilizing activity of both phosphates was associated with a reduction of pH which suggests that the acidification of the culture medium can be one of the mechanisms involved in the solubilization of P. Total number of 27 bacterial strains and 29fungal strains are taken for experiment and studied for maximum solubilization of insoluble inorganic phosphorous.. From the above study, it is concluded that More than 40% isolates of bacterial and fungal strains show the effect of phosphate solubilizing activity. The bacterial strain with 11B and fungal strain with 6F has highest phosphorous solubilization. From the maximum specific growth rate it can be concluded that the microbial isolates 6F and 11B are copiotrophs.

A Fed-Batch Strategy Integrated with Mechanical Activation Improves the Solubilization of Phosphate Rock by Aspergillus niger

Solubilization of phosphate rock (PR) by microorganisms is an environmentally sustainable alternative to chemical processing for production of phosphate fertilizers. The effectiveness of this PR biological solubilization process is driven by the microbial production of organic acids that chelate the cations (mainly calcium) bound to phosphate. However, the biological solubilization efficiency has been limited by the PR solids content of cultivation systems and is still low for practical applications. Here, we propose a fed-batch strategy coupled with mechanical activation to improve the biological solubilization of PR by Aspergillus niger. An initial systematic study of the effect of the particle size of Itafos phosphate rock (IPR), a low reactivity phosphate mineral (P2O5, 20%), on the biological solubilization of phosphorus revealed that the particle size played a key role in IPR solubilization. Increases of available phosphate of up to 57% under submerged cultivation and 45% for solid-state culture wer...

Sustainable carbon sources for microbial organic acid production with filamentous fungi

BackgroundThe organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi.ResultsBefore lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteus were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar.ConclusionsWe showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae.

Microbial organic acid production as carbon dioxide sink.

Mixed-substrate conversions are an under-regarded option to fix carbon dioxide in significant amounts. In such a conversion, carbon dioxide together with one other carbon source such as glucose is converted to a single carbon product. With mixed-substrate conversions, it is possible to incorporate carbon dioxide into products with higher oxidation states than the co-substrate. Using abundant co-substrates such as glucose, glycerol or methanol, it is possible to produce organic acids anaerobically, using CO 2 both as an electron acceptor and as an additional carbon source. Here, we outline the thermodynamic feasibility to produce industrially important organic acids with this approach to provide guidance for future metabolic engineering endeavours.

Microbial production of organic acids by endophytic fungi

Abstract The microbial production of organic acids has been considered as a promising strategy to obtain building-block chemicals from renewable feedstocks such as lignocellulosic agro-industrial wastes. This approach is in accordance with the biorefinery concept where the production of biofuels is integrated to higher-value platform chemicals. However, finding a suitable microbial source and the optimum cultivation conditions remains a challenge for the implementation of such process. Endophytic microorganisms have been explored as a source of novel biochemical compounds for biotechnological applications, but the production of organic acids by endophytic fungi remains to be investigated. Here, the potential of using endophytic fungi for organic acids production has been evaluated by carrying out a screening of 35 fungal strains isolated from the leaves and branches of trees inhabiting two mangroves in the state of Sao Paulo, Brazil. The cultivation of a selected Aspergillus awamori 09 (4) strain under solid-state fermentation (SSF) using a mix of wheat bran and sugarcane bagasse (1:3) resulted in 135.5 mg/g of organic acids, which represents around 7-fold increase when compared to the use of sugarcane bagasse alone. These results indicate the potential of mangrove-associated endophytic fungi for organic acid production under SSF using agro-industrial wastes as feedstock, being compatible with the current bioeconomy demands.

Cover Crops and Soil Phosphorus Availability

ABSTRACTPlants affect soil phosphorus (P) solubility through root exudates, but studies are lacking on species used as relay or cover crops in tropical environments. We evaluated the effect of cover crops on soil phosphorus (P) availability in an oxisol. Ruzigrass (Brachiaria ruziziensis), pearl millet (Pennisetum glaucum), peanut (Arachis hypogaea), crambe (Crambe abyssinica), and sorghum (Sorghum bicolor) were grown in pots with soil. Phosphorus uptake, soil inorganic and organic P, maximum P adsorption capacity, and plant root systems were assessed. When root length density is high, the efficiency of P uptake is low due to root competition. Crambe results in greater soil P availability, while peanut and sorghum decrease the soil maximum P adsorption capacity, probably by exuding or stimulating microbial production of organic acids and phenolic compounds. Hence, crambe, peanut, and sorghum are species that may be of interest to increase P use efficiency in cropping systems.

Protein and metabolic engineering for the production of organic acids

Organic acids are natural metabolites of living organisms. They have been widely applied in the food, pharmaceutical, and bio-based materials industries. In recent years, biotechnological routes to organic acids production from renewable raw materials have been regarded as very promising approaches. In this review, we provide an overview of current developments in the production of organic acids using protein and metabolic engineering strategies. The organic acids include propionic acid, pyruvate, itaconic acid, succinic acid, fumaric acid, malic acid and citric acid. We also expect that rapid developments in the fields of systems biology and synthetic biology will accelerate protein and metabolic engineering for microbial organic acid production in the future.

Microbial Community Stratification Linked to Utilization of Carbohydrates and Phosphorus Limitation in a Boreal Peatland at Marcell Experimental Forest, Minnesota, USA

This study investigated the abundance, distribution, and composition of microbial communities at the watershed scale in a boreal peatland within the Marcell Experimental Forest (MEF), Minnesota, USA. Through a close coupling of next-generation sequencing, biogeochemistry, and advanced analytical chemistry, a biogeochemical hot spot was revealed in the mesotelm (30- to 50-cm depth) as a pronounced shift in microbial community composition in parallel with elevated peat decomposition. The relative abundance of Acidobacteria and the Syntrophobacteraceae, including known hydrocarbon-utilizing genera, was positively correlated with carbohydrate and organic acid content, showing a maximum in the mesotelm. The abundance of Archaea (primarily crenarchaeal groups 1.1c and 1.3) increased with depth, reaching up to 60% of total small-subunit (SSU) rRNA gene sequences in the deep peat below the 75-cm depth. Stable isotope geochemistry and potential rates of methane production paralleled vertical changes in methanogen community composition to indicate a predominance of acetoclastic methanogenesis mediated by the Methanosarcinales in the mesotelm, while hydrogen-utilizing methanogens predominated in the deeper catotelm. RNA-derived pyrosequence libraries corroborated DNA sequence data to indicate that the above-mentioned microbial groups are metabolically active in the mid-depth zone. Fungi showed a maximum in rRNA gene abundance above the 30-cm depth, which comprised only an average of 0.1% of total bacterial and archaeal rRNA gene abundance, indicating prokaryotic dominance. Ratios of C to P enzyme activities approached 0.5 at the acrotelm and catotelm, indicating phosphorus limitation. In contrast, P limitation pressure appeared to be relieved in the mesotelm, likely due to P solubilization by microbial production of organic acids and C-P lyases. Based on path analysis and the modeling of community spatial turnover, we hypothesize that P limitation outweighs N limitation at MEF, and microbial communities are structured by the dominant shrub, Chamaedaphne calyculata, which may act as a carbon source for major consumers in the peatland.

Phosphate solubilising microorganisms: role in phosphorus nutrition of crop plants-A review

Phosphorus is the least mobile nutrient element in plant and soil compared to other essential macronutrients. Root development, stalk, stem strength, flower, seed formation, crop maturity, N-fixation in legumes and crop quality are the attributes associated with phosphorus (P) nutrition. Phosphorus solubilizing microorganisms play role in P nutrition by enhancing its availability to plants through release from inorganic and organic soil P pools by solubilization and mineralization. Principal mechanism in soil for P solubilization is lowering of soil pH by microbial production of organic acids and mineralization of organic P by acid phosphatases. Use of phosphorus solubilizing microorganisms alone or in combination with other beneficial bacteria and mycorrhiza as inoculants increase prospects of direct application of rock phosphate (RP) in P uptake and crop production.

Metabolic engineering ofSaccharomyces cerevisiae for production of carboxylic acids: current status and challenges

To meet the demands of future generations for chemicals and energy and to reduce the environmental footprint of the chemical industry, alternatives for petrochemistry are required. Microbial conversion of renewable feedstocks has a huge potential for cleaner, sustainable industrial production of fuels and chemicals. Microbial production of organic acids is a promising approach for production of chemical building blocks that can replace their petrochemically derived equivalents. Although Saccharomyces cerevisiae does not naturally produce organic acids in large quantities, its robustness, pH tolerance, simple nutrient requirements and long history as an industrial workhorse make it an excellent candidate biocatalyst for such processes. Genetic engineering, along with evolution and selection, has been successfully used to divert carbon from ethanol, the natural endproduct of S. cerevisiae, to pyruvate. Further engineering, which included expression of heterologous enzymes and transporters, yielded strains capable of producing lactate and malate from pyruvate. Besides these metabolic engineering strategies, this review discusses the impact of transport and energetics as well as the tolerance towards these organic acids. In addition to recent progress in engineering S. cerevisiae for organic acid production, the key limitations and challenges are discussed in the context of sustainable industrial production of organic acids from renewable feedstocks.

Microbial production of organic acids: expanding the markets

Microbial production of organic acids is a promising approach for obtaining building-block chemicals from renewable carbon sources. Although some acids have been produced for some time and in-depth knowledge of these microbial production processes has been gained, further microbial production processes seem to be feasible, but large-scale production has not yet been possible. Citric, lactic and succinic acid production exemplify three processes in different stages of industrial development. Although the questions being addressed by current research on these processes are diverging, a comparison is helpful for understanding microbial organic acid production in general. In this article, through analysis of the current advances in production of these acids, we present guidelines for future developments in this fast-moving field.

Evidence for Enhanced Mineral Dissolution in Organic Acid‐Rich Shallow Ground Water

AbstractTotal concentrations of formate, acetate, and isobutyrate varied from less than 5 to greater than 9,000 μmol/l over distances of < 3 m in ground water from a shallow hydrocarbon contaminated aquifer. Laboratory incubations of aquifer material indicate that organic acid concentrations were dependent on the amount of hydrocarbon loading in the sediment and the relative rates of microbial organic acid production and consumption. In heavily contaminated sediments, production greatly exceeded consumption and organic acid concentrations increased. In lightly contaminated sediments rates were essentially equal and organic acid concentrations remained low. Concentrations of dissolved calcium, magnesium, and iron generally were one to two orders of magnitude higher in organic acid‐rich ground water than in ground water having low organic acid concentrations. Carbonate and Fe(III)‐oxyhydroxide minerals were the likely sources of these elements. Similarly, concentrations of dissolved silica, derived from quartz and k‐feldspar, were higher in organic acid‐rich ground water than in other waters. The positive relation (r = 0.60, p < .05, n = 16) between concentrations of silica and organic acids suggests that the microbially mediated buildup of organic acids in ground water enhanced quartz/k‐feldspar dissolution in the aquifer, although it was not the only factor influencing their dissolution. A model that included organic acid microequivalents normalized by cation microequivalents significantly strengthened the correlation (r = 0.79, p < .001, n = 16) between dissolved silica and organic acid concentrations, indicating that competition between silica and cations for complexation sites on organic acids also influenced quartz/k‐feldspar dissolution. Physical evidence for enhanced mineral dissolution in organic acid‐rich waters included scanning electron microscopy images of highly corroded quartz and k‐feldspar grains from portions of the aquifer containing organic acid‐rich ground water. Microporosity generated in hydrocarbon contaminated sediments may adversely affect remediation efforts that depend on the efficient injection of electron acceptors into an aquifer or on the recovery of solutes from an aquifer.

Microbial production of organic acids in aquitard sediments and its role in aquifer geochemistry

Microbial production of organic acids in aquitard sediments and its role in aquifer geochemistry