To improve the silage quality of wilted king grass, the study investigated the effects of Limosilactobacillus fermentum HHL-5 alone and L. fermentum complex citric acid fermentation on wilted king grass silage. Four experimental groups were designed as follows: no additive (CK), citric acid addition (CA), L. fermentum addition (L), and combined L. fermentum and citric acid addition (LCA). The fermentation quality, microbial composition, and aerobic stability of the silage in each group were analyzed. After 30 days of ensiling, LCA had the highest protein content, and L had the lowest ADF content (p < 0.05). Lactic acid and acetic acid contents were significantly increased in the LCA group (p < 0.05), whereas lactic acid content was increased and acetic acid content was significantly decreased in the L group (p < 0.05). Ammonia nitrogen content was significantly decreased in the CA and LCA groups (p < 0.05). The L group was not significantly different from the CK group in terms of bacterial diversity and relative abundance, whereas the LCA group showed markedly higher bacterial diversity and was considerably different from the CK group. The relative abundance of Lactobacillus in the LCA group was higher than that in the L group, while that of Enterobacterales was lower. Compared to the addition of L. fermentum alone, complex citric acid silage significantly enhanced the aerobic stability of this feed. In summary, the application of L. fermentum combined with citric acid can more effectively improve the quality of wilted king grass silage.

Comprehensive utilization of Aspergillus niger waste mycelium based on physically induced autolysis: Preparation of chitosan and alternative nitrogen source

The species Lactococcus lactis is a bacterium extensively used in the dairy industry. This bacterium is Generally Recognized as Safe and was added to the European Food Safety Authority’s Qualified Presumption of Safety list. The major functions of this species in dairy fermentation are the production of lactic acid from lactose, citric acid fermentation, and the hydrolysis of casein. But, the representatives of this species that produce bacteriocin substances can also exert an inhibitory effect against spoilage bacteria. The aims of this study were to test three lactococcal strains isolated from raw goat milk for their postbiotic activity and to test their stability in goat milk yogurts after their application in encapsulated form for their further application. To achieve these aims, validated methods were used. Three Lactococcus lactis strains (identified by Blastn 16S rRNA analysis) produced bacteriocin substances/postbiotics. These concentrated postbiotics inhibited the growth of enterococci and staphylococci (by up to 97.8%), reaching an inhibitory activity of up to 800 AU/mL. The encapsulated (freeze-dried) lactococci survived in the goat milk yogurts with sufficient stability. Strain MK2/8 fortified the yogurts in the highest amount (8.1 ± 0.0 cfu/g log 10). It did not influence the pH of the yogurt.

BackgroundAspergillus tubingensis is a citric acid-producing fungus that can utilize sugars in hydrolysate of lignocellulosic biomass such as sugarcane bagasse and, unlike A. niger, does not produce mycotoxins. To date, no attempt has been made to model its metabolism at genome scale.ResultsHere, we utilized the whole-genome sequence (34.96 Mb length) and the measured biomass composition to reconstruct a genome-scale metabolic model (GSMM) of A. tubingensis DJU120 strain. The model, named iMK1652, consists of 1652 genes, 1657 metabolites and 2039 reactions distributed over four cellular compartments. The model has been extensively curated manually. This included removal of dead-end metabolites and generic reactions, addition of secondary metabolite pathways and several transporters. Several mycotoxin synthesis pathways were either absent or incomplete in the genome, providing a genomic basis for the non-toxinogenic nature of this species. The model was further refined based on the experimental phenotypic microarray (Biolog) data. The model closely captured DJU120 fermentative data on glucose, xylose, and phosphate consumption, as well as citric acid and biomass production, showing its applicability to capture citric acid fermentation of lignocellulosic biomass hydrolysate.ConclusionsThe model offers a framework to conduct metabolic systems biology investigations and can act as a scaffold for integrative modelling of A. tubingensis.

Study on the mechanism of sodium ion inhibiting citric acid fermentation in Aspergillus niger

Enhanced electrokinetic remediation by magnetic induction for the treatment of co-contaminated soil

In today’s industry, about 80% to 90% of citric acid (C6H8O7) production is carried out using submerged fermentation method and Aspergillus niger as citric acid producing microorganism. The use of fermentation method provides advantages, including the utilization of agricultural waste as substrate. Rice husks can be used as substrate in citric acid fermentation because they contain high cellulose and hemicellulose. However, agricultural waste also contains lignin which can interfere with the hydrolysis of cellulose and hemicellulose into reducing sugars, therefore optimisation of pre-treatment process is needed to separate lignin in rice husk. In addition to the optimisation of pre-treatment process, optimisation of fermentation parameter variations to obtain maximum citric acid yield is necessary. Therefore, the aim of this narrative review is to desribe various pre-treatment methods that can be done to remove lignin from rice husks, and to provide information on the benefits of using the Central Composite Design method in the optimisation of various fermentation parameters.

The biosynthesis of citric acid (CA) using Aspergillus niger as a carrier is influenced by mycelium morphology, which is determined by the expression level of morphology-related genes. As a key component of the fungal cell wall, chitin content has an important effect on morphogenesis, and to investigate the effects of this on fermentation performance, we used RNA interference to knockdown chitin synthase C (CHSC) and chitin synthase activator (CHS3) to obtain the single-gene mutant strains A. niger chs3 and chsC and the double mutant A. niger chs3C. We found that the CA fermentation performance of the two single mutants was significantly better than that of the double mutant. The mutant A. niger chs3-4 exhibited CA production potential compared to that of the parent strain in scale-up fermentation; we determined certain characteristics of CA high-yielding strain fermentation pellets. In addition, when chsC alone was silenced, there was very little change in chs3 mRNA levels, whereas those of chsC were significantly reduced when only chs3 was silenced. As this may be because of a synergistic effect between chsC and chs3, and we speculated that the latent activation target of CHS3 is CHSC, our results confirmed this hypothesis. This study is the first application of a separation and combination silence strategy of chitin synthase and chitin synthase activator in the morphology of A. niger CA fermentation. Furthermore, it provides new insights into the method for the morphological study of A. niger fermentation and the interaction of homologous genes. KEY POINTS: • The function of chitin synthase C (chsC) and chitin synthase activator (chs3) is tightly interrelated. • Mycelial morphology was optimized by knockdown of CHS3, resulting in the overproduction of citric acid. • The separation and combination silence strategies are promising tools for the interaction of homologous housekeeping genes.

Online quantitative substrate, product, and cell concentration in citric acid fermentation using near-infrared spectroscopy combined with chemometrics

High-yield citric acid production by the filamentous Ascomycete fungus Aspergillus niger requires a combination of extreme nutritional conditions, of which maintaining a low manganese (II) ion concentration (<5 μg L−1) is a key feature. Technical-scale production of citric acid predominantly uses stainless-steel tank fermenters, but glass bioreactors used for strain improvement and manufacturing process development also contain stainless steel components, in which manganese is an essential alloying element. We show here that during citric acid fermentations manganese (II) ions were leaching from the bioreactor into the growth media, resulting in altered fungal physiology and morphology, and significant reduction of citric acid yields. The leaching of manganese (II) ions was dependent on the fermentation time, the acidity of the culture broth and the sterilization protocol applied. Manganese (II) ion leaching was partially mitigated by electrochemical polishing of stainless steel components of the bioreactor. High concentrations of manganese (II) ions during early cultivation led to a reduction in citric acid yield. However, the effect of manganese (II) ions on the reduction of citric acid yield diminished towards the second half of the fermentation. Since maintaining low concentrations of manganese (II) ions is costly, the results of this study can potentially be used to modify protocols to reduce the cost of citric acid production.

Citric acid is the most important organic acid produced in tonnage and is extensively used in food and pharmaceutical industries. It is produced mainly by submerged fermentation using Aspergillus niger or Candida sp. from different sources of carbohydrates, such as molasses and starch-based media. In view of surges in demand and growing markets, there is always a need for the discovery and development of better production techniques and solutions to improve production yields and the efficiency of product recovery. To support the enormous scale of production, it is necessary and important for the production process to be environmentally friendly by utilizing readily available and inexpensive agro-industrial waste products, while maintaining high production yields. This review article for fermentation of citric acid and Microbial production of citric acid, Substrates and strategies of citric acid production for Surface fermentation, Submerged fermentation, Solid-state fermentation and also the effects of various Factors affecting of citric acid fermentation conditions are Carbon source, Nitrogen limitation, Phosphorus source, Lower Alcohols, pH of culture medium, Trace elements, Aeration and Other factors. citric acid recovery options and the numerous applications of citric acid, based on the literature review information of citric acid production by fermentation technology.

BackgroundGlucose transporters play an important role in the fermentation of citric acid. In this study, a high-affinity glucose transporter (HGT1) was identified and overexpressed in the industrial strain A. niger CGMCC 10142. HGT1-overexpressing strains using the PglaA and Paox1 promoters were constructed to verify the glucose transporter functions.ResultAs hypothesized, the HGT1-overexpressing strains showed higher citric acid production and lower residual sugar contents. The best-performing strain A. niger 20-15 exhibited a reduction of the total sugar content and residual reducing sugars by 16.5 and 44.7%, while the final citric acid production was significantly increased to 174.1 g/L, representing a 7.3% increase compared to A. niger CGMCC 10142. Measurement of the mRNA expression levels of relevant genes at different time-points during the fermentation indicated that in addition to HGT1, citrate synthase and glucokinase were also expressed at higher levels in the overexpression strains.ConclusionThe results indicate that HGT1 overexpression resolved the metabolic bottleneck caused by insufficient sugar transport and thereby improved the sugar utilization rate. This study demonstrates the usefulness of the high-affinity glucose transporter HGT1 for improving the citric acid fermentation process of Aspergillus niger CGMCC 10142.

Abstract Citric acid is consumed in the largest tonnage among organic acids; it is also the second largest fermentation product after ethanol. Citric acid has high economic value due to its numerous applications. The production of citric acid is increasing steadily, along with improved yield efficiency and more advanced technologies. The focus of this review is the two categories of processes producing citric acid using Aspergillus niger, the first starting with whole maize flour and the second starting from maize starch. Alternate substrates and recent methods to improve citric acid fermentation are discussed. The latest patents on production of citric acid are listed and summarized.

The non-grain crop cassava has attracted intense attention in the biorefinery process. However, efficient biorefinery of whole cassava is faced with some challenges due to the existence of strain inhibition and refractory cellulose during the citrate production process. Here, a novel breeding method - atmospheric and room temperature plasma (ARTP) - was applied for strain improvement of citrate-producing strain Aspergillus niger from whole cassava. The citrate yield of the mutant obtained using ARTP mutagenesis increased by 36.5% in comparison with the original strain. Moreover, citric acid fermentation was further improved on the basis of an enhanced co-saccharification strategy by supplementing glucoamylase and cellulase. The fermentation efficiency increased by 35.8% with a 17.0g L-1 reduction in residual sugar on a pilot scale. All these results confirmed that a combination of the novel breeding method and enhanced co-saccharification strategy could be used to efficiently refine whole cassava. The results also provide inspiration for the production of value-added products and waste disposal in agro-based industries. © 2021 Society of Chemical Industry.

Although the management of citrus residues is of concern, their valorization is a challenging alternative. In this work, raw orange juice processing wastewater was spontaneously fermented to determine the succession in microbial communities and identify new indigenous microbial strains of high pectinolytic activity. Pectinolytic strains were isolated using citrus pectin as growth substrate. A shift in fungal population observed during spontaneous fermentation, where the abundances of Hanseniaspora, Cystofilobasidium and Meyerozyma were significantly increased, whereas Pichia fermentans followed by Saccharomyces spp. became the predominant taxa in the fermented wastewater. A significant reduction in the relative abundance of homofermentative aerococci and an increase in the relative abundance of heterofermentative leuconostocs and lactobacilli occurred during fermentation, while enterococci were predominant throughout the fermentation process. Regarding ecological indices, opposite changes took place in the bacterial compared to fungal community structure, but in a less pronounced degree. Examination of beta-diversity revealed the key role of Pichia species in driving fungal community structure during fermentation. P. fermentans, the predominant taxon in the fermented wastewater, was found to be the most effective pectinolytic microorganism. Pectin hydrolysis, carbohydrate fermentation to ethanol, lactic acid and acetate, and citric acid fermentation were the most important factors, influencing microbial community structure.

Combination of steam explosion and ionic liquid pretreatments for efficient utilization of fungal chitin from citric acid fermentation residue

Degradation of the mixture of ethyl formate, propionic aldehyde, and acetone by Aeromonas salmonicida: A novel microorganism screened from biomass generated in the citric acid fermentation industry

Aims: Legumes, (especially indigenous/ underutilized legumes), have been found to make substantial contributions to nutrient intakes of the populace especially in low resources environments. The African yam bean (AYB) is one of such indigenous legumes with utilization constraints such as hard-to-cook phenomenon, beany flavour, bitter taste and some anti- nutritional factors that limit its utilization. The aims of this study were to determine effect of citric acid treatment and fermentation on the chemical composition of African yam bean (Sphenostylisstenocarpa) and sensory evaluation of its gruel.&#x0D; Methodology: Cream coloured AYB seeds were purchased in Enugu, Enugu State Nigeria. Sorted AYB seeds were washed and fermented in citric acid medium (0.25%, 0.5% and 1%) for 24 h 48 h and 72 h at room temperature (28°C) in a seed water ratio of 1:4 (w/v). The control seeds were fermented without citric acid for 24 h, 48 h and 72 h. After fermentation, each batch of the fermented seeds was divided into two. The first half was dehulled and the other half was left as whole. The fermented seeds were separately dried and milled into flour for further use. Standard methods were used for proximate, mineral and anti-nutrient analyses. Gruels were produced from all the flours and subjected to sensory evaluations using a nine-point hedonic scale. Data obtained were analyzed using a Statistical Package for Social Sciences (SPSS) version 20.0. The analysis of variance (ANOVA) was used to compute the mean and standard deviations. Means were compared using the least significant difference (LSD) and significance accepted at P&lt;.05.&#x0D; Results: Chemical compositions of AYB flour fermented in 0.5% citric acid solution showed that protein contents increased by 50%, dietary fibre decreased by 0.02%. Raffinose, stachyose, lectins, trypsin inhibitors, tannins, oxalates, phytates and saponins were all significantly reduced to safe levels. Gruels made from raw and dehulled AYB seeds fermented for 24 h with 0.5% citric acid had higher scores for aroma (7.30 &amp; 7.35, respectively) and general acceptability (7.32 &amp; 7.22, respectively). Dehulled AYB fermented for 24 h in 1% citric acid had the highest score (7.99) for colour. Based on the sensory evaluation results, gruels made from the AYB seeds fermented in 0.5% citric acid compared with the gruels made from AYB seeds that were fermented in tap water. The results showed that gruels made from the AYB seeds that were fermented in 0.5% citric acid for 24 h had higher score for aroma (7.70), colour (7.10) and overall acceptability (7.52). Utilization of AYB in food formulation could be improved by fermenting in 0.5% citric acid solution for 24 h.

In order to alleviate the environmental pollution caused by raw citric acid fermentation waste (CAFW) and reduce the dependence of polyurethane foam production on petroleum-based materials, a facil...

Feasibility of multi-hydrolytic enzymes production from optimized grape pomace residues and wheat bran mixture using Aspergillus niger in an integrated citric acid-enzymes production process