Cleavage of α-1,4-glycosidic linkages by the glycosylphosphatidylinositol-anchored α-amylase AgtA decreases the molecular weight of cell wall α-1,3-glucan in Aspergillus oryzae

Biological and biochemical studies on cell surface functions in microorganisms used in brewing and fermentation industry

When brewing microorganisms, which include bacteria and fungi, act on solid cereal substrates, the microbial cell surface interacts with the substrate. When microorganisms use sugars and amino acids released by hydrolysis of the substrate, this occurs on the cell surface. Throughout my career, I have focused on functional studies of cell surface molecules such as solute transporters, cell wall components, and bio-surfactants and applied the knowledge obtained to the development of fermentation technologies. In this review, I describe (i) catabolite control by sugar transporters and energy generation coupled with amino acid decarboxylation in lactic acid bacteria; (ii) recruitment of a polyesterase by the fungal bio-surfactant proteins to polyesters and subsequent promotion of polyester hydrolysis; and (iii) hyphal aggregation via cell wall α-1,3-glucan and galactosaminogalactan in aspergilli and the development of a novel liquid culture method with hyphal dispersed mutants lacking these two polysaccharides.

Chitosan: An overview of its properties, solubility, functional technologies, food and health applications

The properties and potential applications of chitosan have attracted a lot of interest; each year, the number of publications and patents based on this polymer increases. A significant obstacle to the application of chitosan is its limited solubility in basic and neutral solutions. The fact that chitosan is a series of molecules with variations in size, content, and monomer distribution rather than a single polymer with a well-defined structure and a natural origin is another significant barrier. Some of the claimed biological qualities are distinct, and these characteristics have a fundamental effect on the polymer's technological and biological performance. The poor solubility of the polymer can be improved by chitosan chemistry, and in this assessment, we discuss the changes made to make chitosan more soluble and its possible uses. We concentrate on a few of the primary biological characteristics of chitosan and how they relate to the physicochemical characteristics of the polymer. The use of chitosan in the environmentally friendly manufacture of metallic nanoparticles as well as its usage as a booster for biocatalysts are two further applications of polymers that are linked to green processes that we revisit. This study also presents information about utilizing chitosan's technological advantages.

Phenotypic landscape of a fungal meningitis pathogen reveals its unique biology

Cryptococcus neoformans is the most common cause of fungal meningitis and the top-ranked W.H.O. priority fungal pathogen. Only distantly related to model fungi, C. neoformans is also a powerful experimental system for exploring conserved eukaryotic mechanisms lost from specialist model yeast lineages. To decipher its biology globally, we constructed 4328 gene deletions and measured-with exceptional precision--the fitness of each mutant under 141 diverse growth-limiting in vitro conditions and during murine infection. We defined functional modules by clustering genes based on their phenotypic signatures. In-depth studies leveraged these data in two ways. First, we defined and investigated new components of key signaling pathways, which revealed animal-like pathways/components not predicted from studies of model yeasts. Second, we identified environmental adaptation mechanisms repurposed to promote mammalian virulence by C. neoformans, which lacks a known animal reservoir. Our work provides an unprecedented resource for deciphering a deadly human pathogen.

The postbiotic potential of Aspergillus oryzae - a narrative review

The filamentous fungus Aspergillus oryzae has a long tradition in East Asian food processing. It is therefore not surprising that in recent years fermentation products of A. oryzae have attracted attention in the emerging field of postbiotics. This review aims to provide a comprehensive summary of the potential postbiotic effects of fermentation products from A. oryzae, by discussing possible mechanisms of action against the background of the molecular composition determined so far. In particular, cell wall constituents, enzymes, extracellular polymeric substances, and various metabolites found in A. oryzae fermentation preparations are described in detail. With reference to the generally assumed key targets of postbiotics, their putative beneficial bioactivities in modulating the microbiota, improving epithelial barrier function, influencing immune responses, metabolic reactions and signaling through the nervous system are assessed. Drawing on existing literature and case studies, we highlight A. oryzae as a promising source of postbiotics, particularly in the context of animal health and nutrition. Challenges and opportunities in quality control are also addressed, with a focus on the necessity for standardized methods to fully harness the potential of fungal-based postbiotics. Overall, this article sheds light on the emerging field of A. oryzae-derived postbiotics and emphasizes the need for further research to fully realize their therapeutic potential.

Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

Controlling the stereoselectivity of 1,2-cis glycosylation is one of the most challenging tasks in the chemical synthesis of glycans. There are various 1,2-cis glycosides in nature, such as α-glucoside and β-mannoside in glycoproteins, glycolipids, proteoglycans, microbial polysaccharides, and bioactive natural products. In the structure of polysaccharides such as α-glucan, 1,2-cis α-glucosides were found to be the major linkage between the glucopyranosides. Various regioisomeric linkages, 1→3, 1→4, and 1→6 for the backbone structure, and 1→2/3/4/6 for branching in the polysaccharide as well as in the oligosaccharides were identified. To achieve highly stereoselective 1,2-cis glycosylation, including α-glucosylation, a number of strategies using inter- and intra-molecular methodologies have been explored. Recently, Zn salt-mediated cis glycosylation has been developed and applied to the synthesis of various 1,2-cis linkages, such as α-glucoside and β-mannoside, via the 1,2-cis glycosylation pathway and β-galactoside 1,4/6-cis induction. Furthermore, the synthesis of various structures of α-glucans has been achieved using the recent progressive stereoselective 1,2-cis glycosylation reactions. In this review, recent advances in stereoselective 1,2-cis glycosylation, particularly focused on α-glucosylation, and their applications in the construction of linear and branched α-glucans are summarized.