Review on production of citric acid by fermentation technology

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.

Aspergillus oryzae Grown on Rice Hulls Used as an Additive for Pretreatment of Starch-Containing Wastewater from the Pulp and Paper Industry

From an industrial point of view, the use of microorganisms as a wastewater bioremediation practice represents a sustainable and economic alternative for conventional treatments. In this work, we investigated the starch bioremediation of paper mill wastewater (PMW) with Aspergillus oryzae. This amylase-producing fungus was tested in submerged fermentation technology (SmF) and solid-state fermentation (SSF) on rice hulls. The tests were conducted to assay the concentration of the reducing sugars on paper mill wastewater. The bioremediation of starch in the wastewater was carried out by A. oryzae, which proved capable of growing in this complex media as well as expressing its amylase activity.

Efficient anaerobic consumption of D-xylose by E. coli BL21(DE3) via xylR adaptive mutation

Background Microorganisms can prioritize the uptake of different sugars depending on their metabolic needs and preferences. When both D-glucose and D-xylose are present in growth media, E. coli cells typically consume D-glucose first and then D-xylose. Similarly, when E. coli BL21(DE3) is provided with both D-glucose and D-xylose under anaerobic conditions, glucose is consumed first, whereas D-xylose is consumed very slowly. Results When BL21(DE3) was adaptively evolved via subculture, the consumption rate of D-xylose increased gradually. Strains JH001 and JH019, whose D-xylose consumption rate was faster, were isolated after subculture. Genome analysis of the JH001 and JH019 strains revealed that C91A (Q31K) and C740T (A247V) missense mutations in the xylR gene (which encodes the XylR transcriptional activator), respectively, controlled the expression of the xyl operon. RT-qPCR analyses demonstrated that the XylR mutation caused a 10.9-fold and 3.5-fold increase in the expression of the xylA (xylose isomerase) and xylF (xylose transporter) genes, respectively, in the adaptively evolved JH001 and JH019 strains. A C91A adaptive mutation was introduced into a new BL21(DE3) background via single-base genome editing, resulting in immediate and efficient D-xylose consumption. Conclusions Anaerobically-adapted BL21(DE3) cells were obtained through short-term adaptive evolution and xylR mutations responsible for faster D-xylose consumption were identified, which may aid in the improvement of microbial fermentation technology.

Fermentation quality of herbal tea residue and its application in fattening cattle under heat stress

Background Herbal tea residue (HTR) is generally considered to be the waste of herbal tea beverage production while it still retains rich nutrients and active substances. The main aim of the present study was to investigate the effect of fermentation technology on improving the quality of HTRs, and focus on the fermented HTR-induced alleviation of summer heat stress in fattening cattle. Results In this study, the waste HTR was fermented and then fed to a total of 45 fattening cattle that were divided into 3 groups (fermented HTR replaced 0, 15, 30% of the forage component of the diet), and the feeding experiment was lasted for 40 days. The physiological indexes, growth performance and fecal microbiota of fattening cattle were evaluated and results showed that fermented HTR could effectively reduce the respiratory rate and rectal temperature of fattening cattle under heat stress, increase the daily feed intake and daily gain, and improve the antioxidant content and blood immune index. In addition, we studied the fecal microbiota composition of 6 fattening cattle in control and 30% HTR substitution groups and found fermented HTR significantly changed the composition of fecal microbiota and increased microbial diversity, and correlation analysis suggested that the bacteria were closely related to fecal SCFA levels of fattening cattle under heat stress. Conclusions In this study, fermented HTR replaced 30% of the forage component of the diet that can change the intestine microorganisms, maintain health and alleviate the heat stress of fattening cattle.

Efficient Anaerobic Consumption of D-xylose by E. coli BL21(DE3) via xylR Adaptive Mutation

Background: Microorganisms can prioritize the uptake of different sugars depending on their metabolic needs and preferences. When both D-glucose and D-xylose are present in growth media, E. coli cells typically consume D-glucose first and then D-xylose. Similarly, when E. coli BL21(DE3) is provided with both glucose and xylose under anaerobic conditions, glucose is consumed first, whereas xylose is consumed very slowly.Results: When BL21(DE3) was adaptively evolved via subculture, the consumption rate of D-xylose increased gradually. Strains JH001 and JH019, whose D-xylose consumption rate was faster, were isolated after subculture. Genome analysis of the JH001 and JH019 strains revealed that C91A (Q31K) and C740T (A247V) missense mutations in the xylR gene (which encodes the XylR transcriptional activator), respectively, controlled the expression of the xyl operon. RT-qPCR analyses demonstrated that the XylR mutation caused a 10.9-fold and 3.5-fold increase in the expression of the xylA (xylose isomerase) and xylF (xylose transporter) genes, respectively, in the adaptively evolved JH001 and JH019 strains. A C91A adaptive mutation was introduced into a new BL21(DE3) background via single-base genome editing, resulting in immediate and efficient D-xylose consumption. Conclusions: We obtained anaerobically-adapted BL21(DE3) cells through short-term adaptive evolution and identified xylR mutations responsible for faster xylose consumption, which may facilitate the improvement of microbial fermentation technology.

Regulation of Structure and Quality of Dried Noodles by Liquid Pre-Fermentation

Liquid pre-fermentation technology was innovatively applied to the development of dried fermented noodles. The effects of fermentation time (1, 3 and 6 h) and yeast addition (0.2, 0.5 and 1.0 g/100 g of flour) on the quality, microstructure and flavor of dried noodles were also investigated in this study. Conspicuous porous structures and greater thickness of dried noodles were found when the fermentation time was ≤ 3 h and the yeast addition was ≥ 0.5 g/100 g of flour, which contributed to the increase in the breaking strength, cooking time and water absorption. However, when the fermentation time increased to 6 h, finer microporous structures, little change related to thickness and richer flavor levels were detected. Additionally, the total titratable acidity of dried fermented noodles was increased to 3.38–4.43 mL compared with the unfermented noodles (2.15 mL). Weaker gluten network structures caused by long-time fermentation and acidic environment led to lower hardness, chewiness, tensile force and tensile distance of cooked fermented noodles.

Fermentation Quality of Herbal Tea Residue and its Application in Fattening Cattle Under Heat Stress

Background: Herbal tea residue (HTR) is generally considered to be the waste of herbal tea beverage production while it still retains rich nutrients and active substances. The main aim of the present study was to investigate the effect of fermentation technology on improving the quality of HTRs, and focus on the fermented HTR-induced alleviation of summer heat stress in fattening cattle.Results: In this study, the waste HTR was fermented and then fed to a total of 45 fattening cattles that were divided into 3 groups (fermented HTR replaced 0%, 15%, 30% of Pennisetum purpureum respectively), and the feeding experiment was lasted for 40 days. The physiological indexes, growth performance and fecal microorganisms of fattening cattle were evaluated and results showed that fermented HTR could effectively reduce the respiratory rate and rectal temperature of fattening cattle under heat stress, increase the daily feed intake and daily gain, and improve the antioxidant content and blood immune index. In addition, we studied the fecal microorganisms composition of 6 fattening cattles in each group and found fermented HTR significantly changed the composition of fecal microorganisms and increased microbial diversity, and correlation analysis suggested that the bacteria were closely related to fecal SCFA levels of fattening cattle under heat stress. Conclusions: we suggested that 30% of fermented HTR can help maintain health of fattening cattle and alleviate the heat stress of fattening cattle by the change of intestine microorganisms.