Transcriptome analysis of Rhizopus oryzae seed pellet formation using triethanolamine

A review: Effects of microbial fermentation on the structure and bioactivity of polysaccharides in plant-based foods

Fermented plant-based foods that catering to consumers' diverse dietary preferences play an important role in promoting human health. Recent exploration of their nutritional value has sparked increasing interest in the structural and bioactive changes of polysaccharides during fermentation, the essential components of plant-based foods which have been extensively studied for their structures and functional properties. Based on the latest key findings, this review summarized the dominant fermented plant-based foods in the market, the involved microbes and plant polysaccharides, and the corresponding modification in polysaccharides structure. Further microbial utilization of these polysaccharides, influencing factors, and the potential contributions of altered structure to the functions of polysaccharides were collectively illustrated. Moreover, future research trend was proposed, focusing on the directional modification of polysaccharides and exploration of the mechanisms underlying structural changes and enhanced biological activity during fermentation.

Improving the productivity of gibberellic acid by combining small-molecule compounds-based targeting technology and transcriptomics analysis in Fusarium fujikuroi

Gibberellic acid (GA3), produced industrially by Fusarium fujikuroi, stands as a crucial plant growth regulator extensively employed in the agriculture filed while limited understanding of the global metabolic network hinders researchers from conducting rapid targeted modifications. In this study, a small-molecule compounds-based targeting technology was developed to increase GA3 production. Firstly, various small molecules were used to target key nodes of different pathways and the result displayed that supplement of terbinafine improved significantly GA3 accumulation, which reached to 1.08 g/L. Subsequently, lipid and squalene biosynthesis pathway were identified as the key pathways influencing GA3 biosynthesis by transcriptomic analysis. Thus, the strategies including in vivo metabolic engineering modification and in vitro supplementation of lipid substrates were adopted, both contributed to an enhanced GA3 yield. Finally, the engineered strain demonstrated the ability to achieve a GA3 yield of 3.24 g/L in 5 L bioreactor when utilizing WCO as carbon source and feed.

Intensification of bioprocesses with filamentous microorganisms

Many industrial biotechnological processes use filamentous microorganisms to produce platform chemicals, proteins, enzymes and natural products. Product formation is directly linked to their cellular morphology ranging from dispersed mycelia over loose clumps to compact pellets. Therefore, the adjustment and control of the filamentous cellular morphology pose major challenges for bioprocess engineering. Depending on the filamentous strain and desired product, optimal morphological shapes for achieving high product concentrations vary. However, there are currently no overarching strain- or product-related correlations to improve process understanding of filamentous production systems. The present book chapter summarizes the extensive work conducted in recent years in the field of improving product formation and thus intensifying biotechnological processes with filamentous microorganisms. The goal is to provide prospective scientists with an extensive overview of this scientifically diverse, highly interesting field of study. In the course of this, multiple examples and ideas shall facilitate the combination of their acquired expertise with promising areas of future research. Therefore, this overview describes the interdependence between filamentous cellular morphology and product formation. Moreover, the currently most frequently used experimental techniques for morphological structure elucidation will be discussed in detail. Developed strategies of morphology engineering to increase product formation by tailoring and controlling cellular morphology and thus to intensify processes with filamentous microorganisms will be comprehensively presented and discussed.

Improving the productivity of malic acid by alleviating oxidative stress during Aspergillus niger fermentation

BACKGROUND

As an attractive platform chemical, malic acid has been commonly used in the food, feed and pharmaceutical field. Microbial fermentation of biobased sources to produce malic acid has attracted great attention because it is sustainable and environment-friendly. However, most studies mainly focus on improving yield and ignore shortening fermentation time. A long fermentation period means high cost, and hinders the industrial applications of microbial fermentation. Stresses, especially oxidative stress generated during fermentation, inhibit microbial growth and production, and prolong fermentation period. Previous studies have shown that polypeptides could effectively relieve stresses, but the underlying mechanisms were poorly understood.

RESULTS

In this study, polypeptides (especially elastin peptide) addition improves the productivity of malic acid in A. niger, resulting in shortening of fermentation time from 120 to 108 h. Transcriptome and biochemical analyses demonstrated that both antioxidant enzyme-mediated oxidative stress defense system, such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and nonenzymatic antioxidant system, such as glutathione, were enhanced in the presence of elastin peptide, suggesting elastin peptide relieving oxidative stresses is involved in many pathways. In order to further investigate the relationship between oxidative stress defense and malic acid productivity, we overexpressed three enzymes (Sod1, CAT, Tps1) related to oxidation resistance in A. niger, respectively, and these resulting strains display varying degree of improvement in malic acid productivity. Especially, the strain overexpressing the Sod1 gene achieved a malate titer of 91.85 ± 2.58 g/L in 96 h, corresponding to a productivity of 0.96 g/L/h, which performs better than elastin peptide addition.

CONCLUSIONS

Our investigation provides an excellent reference for alleviating the stress of the fungal fermentation process and improving fermentation efficiency.