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Soy sauce is a traditional condiment that undergoes microbial fermentation of various ingredients to achieve its desired color, scent, and flavor. Sporidiobolus pararoseus , which is a type of Rhodocerevisiae , shows promising potential as a source of lipids, carotenoids, and enzymes that can enrich the taste and color of soy sauce. However, there is currently a lack of systematic and comprehensive studies on the functions and mechanisms of action of S. pararoseus during soy sauce fermentation. In this review, it is well established that S. pararoseus produces lipids that are abundant in unsaturated fatty acids, particularly oleic acid, as well as various carotenoids, such as β-carotene, torulene, and torularhodin. These pigments are synthesized through the mevalonic acid pathway and possess remarkable antioxidant properties, acting as natural colorants. The synthesis of carotenoids is stimulated by high salt concentrations, which induces oxidative stress caused by NaCl. This stress further activates crucial enzymes involved in carotenoid production, ultimately leading to pigment formation. Moreover, S. pararoseus can produce high-quality enzymes that aid in the efficient utilization of soy sauce substrates during fermentation. Furthermore, this review focused on the impact of S. pararoseus on the color and quality of soy sauce and comprehensively analyzed its characteristics and ingredients. Thus, this review serves as a basis for screening high-quality oleaginous red yeast strains and improving the quality of industrial soy sauce production through the wide application of S. pararoseus. • The synthesis pathway of lipids and carotenoids in S. pararoseus was illustrated. • S. pararoseus can compensate for lipid insufficiency during fermentation. • S. pararoseus can produce carotenoids under various environmental stresses. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • M. purpuresus M183, generated by ARTP, with pigments production of 8460 U/g. • Response surface methodology applied significantly enhanced the MPs production. • Immobilization fermentation operated by utilization of 3% sodium alginate. • A simultaneous fermentation process and separation system was established for MPs. Abstract A mutant Monascus purpureus strain, M183, which produced monascus pigments (MPs) at 8460 U/g via solid-state batch-fermentation, was generated using the atmospheric and room temperature plasma (ARTP) mutation system. The optimal glucose concentration (80 g/L) in traditional fermentation media that yielded the highest MPs productivity was determined. Response surface methodology (RSM) was applied to maximize MPs production using liquid-state batch-fermentation. Under optimal conditions (0.58 g/L MgSO 4 ·7H 2 O, 0.02 g/L ZnSO 4 ·7H 2 O, 0.02 g/L FeSO 4 ·7H 2 O and 4.85 g/L NH 4 NO 3), 207.67 U/mL of MPs were produced with 98.12% validity based on the predicted value. Extracellular MPs production increased significantly to 35.52 U/mL, compared to 14.19 U/mL of the original strain, M. purpureus LQ-6. M. purpureus spores immobilized in sodium alginate were studied. A simultaneous fermentation and separation system was established for MPs using the novel absorption resin LX300C to enhance production efficiency of extracellular MPs. [ABSTRACT FROM AUTHOR]

• Yeast extract amino acids can shape the fermentation microbiota of soy sauce. • Yeast extract amino acids boost the competitiveness of aroma-producing microbiota. • The best mass ratio of neutral: acidic: basic amino acids is 58:27:15. • The best amino acid formula can increase the malt aroma of soy sauce by 52.6%. Yeast extracts, of which amino acids are the main component, can be directly applied to improve the flavor of final soy sauce. In this study, the potential of commercial yeast extracts was explored from amino acid approach to enhance the flavor quality of soy sauce by shaping the core fermentation microbiota. Alkaline and neutral amino acids favored the competitive benefits of flavor-producing bacteria, while acidic amino acids promoted the stress resistance of the fermentation microbiota, especially the abundance of Lactobacillus , which increased to 18.03–23.78% and became the predominant microbiota. The mass ratio of neutral-nonpolar: neutral-polar: acidic: alkaline amino acids was 40: 18: 27: 15, which provided the optimal improvement of soy sauce aroma. The formulation and activated the metabolic pathways of 3-methyl-1-butyraldehyde, 3-methyl-1-butanol and 2-methyl-1-propanol through Leu and Ile, resulting in a 52.6% increase in malt-like aroma. This study provides a new idea for the regulation of soy sauce fermentation. [ABSTRACT FROM AUTHOR]

Monascus pigments (MPs), the secondary metabolites produced by the fungal strains of Monascus spp., hold commercial importance in not only the food and meat industries, but also therapeutic, cosmetic, and textile industries. To reduce the cost of MPs production, the utilization of rice straw hydrolysate as a substrate in submerged fermentation was investigated. The atmospheric and room temperature plasma (ARTP) mutation system was employed to develop a mutant strain Monascus purpureus M630, with high total extracellular Monascus pigments (exMPs) production of 34.12 U/mL in submerged fermentation with glucose-based medium. The results revealed that M. purpureus M630 produces 8.61 U/mL and 20.86 U/mL of exMPs in rice straw hydrolysate alone or in combination with glucose fermentation medium, respectively. Furfural (Fur) and 5′-hydroxymethyl furfural (5′-HMF), produced during pretreatment and hydrolysis of rice straw; are generally inhibitory for microbial growth and fermentation. Our findings revealed that M. purpureus M630 develops the tolerance and adaptation mechanisms in response to 5′-HMF and Fur during growth and MPs biosynthesis in rice straw hydrolysate. In conclusion, we report that rice straw hydrolysate can serve as an efficient and low-cost substitute for the MP production through submerged fermentation by Monascus spp. Image 1 • High exMP-producing mutant strain Monascus purpureus M630 was developed by ARTP. • Rice straw hydrolysate is an effective substrate for producing Monascus pigments. • M. purpureus M630 exhibits high tolerance and adaptation towards 5′-HMF and Fur. [ABSTRACT FROM AUTHOR]

Abstract Fermentation material fluid mixing is an indispensable subsidiary technology for modern biogas engineering, which can increase fermentation efficiency substantially. Taking advantage of computational fluid dynamics (CFD), the flowing progress of biogas fermentation material fluid in the anaerobic digesters can be reappeared, the distribution curve of flow pattern can be obtained, the visualization of flow pattern can be achieved, the features and defect of flow configuration can be differentiated on the basis of the flow pattern visualization. Scholars quantified and evaluated advantages and disadvantages of fermentation material fluid mixing schemes by using CFD and setting the parameters of "poor mixing zone", "dead zone" and so on, which became the important basis of modern biogas engineering design. Meanwhile, the mixing form and running parameters can be excellently designed and thus no longer added at random. On the basis of the classic k-ε model, researchers have developed a variety of improved models, which are more suitable for complex and diverse conditions of biogas fermentation material fluid. In this present study, the applicable algorithm models of various working conditions are proposed after subdivision research. During the first decade of the 21st century, one research upsurge of simulating biogas fermentation material mixing by using the CFD simulation is growing up in the biogas field, which makes a great progress on the aspect of optimal design of digesters shape, mixing form, mixing running parameters and methods of fluid, promotes the research levels of biogas science and becomes one of the most important stage of the biogas science phylogeny. All of these represent the development direction of future, accordingly, the summary of progress related with above research aspects is given in this present study. Graphical abstract fx1 Highlights • The measured results of many flow field parameters can be fitted with simulation. • The methods of setting the mixing parameters by CFD are listed. • Successful examples of optimization of biogas engineering design by CFD are presented. • The applicable algorithm models of various working conditions are proposed. • The role of CFD in promoting the upgrading of biogas project is discussed. [ABSTRACT FROM AUTHOR]

Extractive fermentation has been proven to be efficient in enhancing the secretion and production of secondary metabolites in submerged fermentation by Monascus spp., owing to increased cell membrane permeability and resolved product inhibition. In this study, we investigated the regulation effect of Triton X-100 on cell growth and secondary metabolite biosynthesis in submerged fermentation of M. purpureus DK. The results show that the maximum monascus pigments (MPs), citrinin (CIT) production, and specific growth rate are 136.86 U/mL, 4.57 mg/L, and 0.04 h−1, respectively, when 3 g/L of Triton X-100 is supplemented after fermentation for 10 d, and the extracellular MPs and CIT increased by 127.48% and 288.57%, respectively. RT-qPCR shows that the expression levels of MPs and CIT biosynthesis gene clusters are significantly upregulated, whereas those of glycolysis, tricarboxylic acid cycle, respiratory chains, and ATP synthase are downregulated. This study provides a vital strategy for extractive fermentation under extreme environmental conditions for further enhancing MP production. • In-depth extractive fermentation was enabled. • Secondary metabolites productions were significantly enhanced. • Ethanol and acetate metabolism were analyzed in Monascus. • Overview of disrupted metabolism pathways was shown. [ABSTRACT FROM AUTHOR]

Butanol is an important industrial chemical and an attractive transportation fuel. However, the deficiency of reducing equivalents NAD(P)H in butanol fermentation results in a large quantity of oxidation products, which is a major problem limiting the atom economy and economic viability of bio-butanol processes. Here, we integrated the butanol fermentation process with a NADH-generating, acetoin biosynthesis process to improve the butanol production. By overexpressing the α-acetolactate decarboxylase gene alsD from Bacillus subtilis in Clostridium acetobutylicum , acetoin yield was significantly increased at the cost of acetone. After optimization of fermentation conditions, butanol (12.9 g/L), acetoin (6.5 g/L), and ethanol (1.9 g/L) were generated by the recombinant strain, with acetone no more than 1.8 g/L. Thus, both mass yield and product value were greatly improved. This study demonstrates that reducing power compensation is effective to improve the atom economy of butanol fermentation, and provides a novel approach to improve the economic viability of bio-butanol production. [ABSTRACT FROM AUTHOR]