Use of Residual Biomass from the Textile Industry as Carbon Source for Production of a Low-Molecular-Weight Xylanase from Aspergillus oryzae

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.

Penicillium polonicum a new isolate obtained from Cerrado soil as a source of carbohydrate-active enzymes produced in response to sugarcane bagasse

Penicillium species have been studied as producers of plant cell wall degrading enzymes to deconstruct agricultural residues and to be applied in industrial processes. Natural environments containing decaying plant matter are ideal places for isolating fungal strains with cellulolytic and xylanolytic activities. In the present study, Cerrado soil samples were used as source of filamentous fungi able to degrade xylan and cellulose. Penicillium was the most abundant genus among the obtained xylan and carboxymethylcellulose degraders. Penicillium polonicum was one of the best enzyme producers in agar-plate assays. In addition, it secretes CMCase, Avicelase, pectinase, mannanase, and xylanase during growth in liquid media containing sugarcane bagasse as carbon source. The highest value for endo-β-1,4-xylanase activity was obtained after 4 days of growth. Xyl PP, a 20 kDa endo-β-1,4-xylanase, was purified and partially characterized. The purified enzyme presented the remarkable feature of being resistant to the lignin-derived phenolic compounds, p-coumaric and trans-ferulic acids. This feature calls for its further use in bioprocesses that use lignocellulose as feedstock. Furthermore, future work should explore its structural features which may contribute to the understanding of the relationship between its structure and resistance to phenolic compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03405-x.

Assembling mini-xylanosomes with Clostridium thermocellum XynA, and their properties in lignocellulose deconstruction

Lignocellulose is a prominent source of carbohydrates to be used in biorefineries. One of the main challenges associated with its use is the low yields obtained during enzymatic hydrolysis, as well as the high cost associate with enzyme acquisition. Despite the great attention in using the fraction composed by hexoses, nowadays, there is a growing interest in enzymatic blends to deconstruct the pentose-rich fraction. Among the organisms studied as a source of enzymes to lignocellulose deconstruction, the anaerobic bacterium Clostridium thermocellum stands out. Most of the remarkable performance of C. thermocellum in degrading cellulose is related to its capacity to assemble enzymes into well-organized enzymatic complexes, cellulosomes. A mini-version of a cellulosome was designed in the present study, using the xylanase XynA and the N-terminus portion of scaffolding protein, mCipA, harboring one CBM3 and two cohesin I domains. The formed mini-xylanosome displayed maximum activity between 60 and 70 °C in a pH range from 6 to 8. Although biochemical properties of complexed/non-complexed enzymes were similar, the formed xylanosome displayed higher hydrolysis at 60 and 70 °C for alkali-treated sugarcane bagasse. Lignocellulose deconstruction using fungal secretome and the mini-xylanosome resulted in higher d-glucose yield, and the addition of the mCipA scaffolding protein enhanced cellulose deconstruction when coupled with fungal enzymes. Results obtained in this study demonstrated that the assembling of xylanases into mini-xylanosomes could improve sugarcane deconstruction, and the mCipA protein can work as a cellulose degradation enhancer.

Preparation of β(1→3)/β(1→4) xylooligosaccharides from red alga dulse by two xylanases from Streptomyces thermogriseus

Red alga dulse contains xylan with β(1→3)/β(1→4) linkages. We previously prepared xylooligosaccharides (XOSs) from dulse xylan; however, the product contained many D-xylose residues and fewer XOSs with β(1→3) linkages. To improve the efficiency of XOS production, we prepared two recombinant endoxylanases from Streptomyces thermogriseus (StXyl10 and StXyl11). Comparing the kcat/Km values for dulse xylan, this value from StXyl10 was approximately two times higher than that from StXyl11. We then determined the suitable conditions for XOS production. As a result, dulse XOS was prepared by the successive hydrolysis of 10 mg/mL dulse xylan by 0.5 μg/mL StXyl10 for 4 h at 50 °C and then 2.0 μg/mL StXyl11 for 36 h at 60 °C. Xylan was converted into 95.8% XOS, including 59.7% XOS with a β(1→3) linkage and 0.97% D-xylose. Our study provides useful information for the production of XOSs with β(1→3) linkages.

Conversion of Wheat Bran to Xylanases and Dye Adsorbent by Streptomyces thermocarboxydus

Agro-byproducts can be utilized as effective and low-cost nutrient sources for microbial fermentation to produce a variety of usable products. In this study, wheat bran powder (WBP) was found to be the most effective carbon source for xylanase production by Streptomyces thermocarboxydus TKU045. The optimal media for xylanase production was 2% (w/v) WBP, 1.50% (w/v) KNO₃, 0.05% (w/v) MgSO₄, and 0.10% (w/v) K₂HPO₄, and the optimal culture conditions were 50 mL (in a 250 mL-volume Erlenmeyer flask), initial pH 9.0, 37 °C, 125 rpm, and 48 h. Accordingly, the highest xylanase activity was 6.393 ± 0.130 U/mL, 6.9-fold higher than that from un-optimized conditions. S. thermocarboxydus TKU045 secreted at least four xylanases with the molecular weights of >180, 36, 29, and 27 kDa when cultured on the WBP-containing medium. The enzyme cocktail produced by S. thermocarboxydus TKU045 was optimally active over a broad range of temperature and pH (40–70 °C and pH 5–8, respectively) and could hydrolyze birchwood xylan to produce xylobiose as the major product. The obtained xylose oligosaccharide (XOS) were investigated for 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and the growth effect of lactic acid bacteria. Finally, the solid waste from the WBP fermentation using S. thermocarboxydus TKU045 revealed the high adsorption of Congo red, Red 7, and Methyl blue. Thus, S. thermocarboxydus TKU045 could be a potential strain to utilize wheat bran to produce xylanases for XOS preparation and dye adsorbent.

Analysis of the Transcriptome in Aspergillus tamarii During Enzymatic Degradation of Sugarcane Bagasse

The production of bioethanol from non-food agricultural residues represents an alternative energy source to fossil fuels for incorporation into the world's economy. Within the context of bioconversion of plant biomass into renewable energy using improved enzymatic cocktails, Illumina RNA-seq transcriptome profiling was conducted on a strain of Aspergillus tamarii, efficient in biomass polysaccharide degradation, in order to identify genes encoding proteins involved in plant biomass saccharification. Enzyme production and gene expression was compared following growth in liquid and semi-solid culture with steam-exploded sugarcane bagasse (SB) (1% w/v) and glucose (1% w/v) employed as contrasting sole carbon sources. Enzyme production following growth in liquid minimum medium supplemented with SB resulted in 0.626 and 0.711 UI.mL^-1 xylanases after 24 and 48 h incubation, respectively. Transcriptome profiling revealed expression of over 7120 genes, with groups of genes modulated according to solid or semi-solid culture, as well as according to carbon source. Gene ontology analysis of genes expressed following SB hydrolysis revealed enrichment in xyloglucan metabolic process and xylan, pectin and glucan catabolic process, indicating up-regulation of genes involved in xylanase secretion. According to carbohydrate-active enzyme (CAZy) classification, 209 CAZyme-encoding genes were identified with significant differential expression on liquid or semi-solid SB, in comparison to equivalent growth on glucose as carbon source. Up-regulated CAZyme-encoding genes related to cellulases (CelA, CelB, CelC, CelD) and hemicellulases (XynG1, XynG2, XynF1, XylA, AxeA, arabinofuranosidase) showed up to a 10-fold log2FoldChange in expression levels. Five genes from the AA9 (GH61) family, related to lytic polysaccharide monooxygenase (LPMO), were also identified with significant expression up-regulation. The transcription factor gene XlnR, involved in induction of hemicellulases, showed up-regulation on liquid and semi-solid SB culture. Similarly, the gene ClrA, responsible for regulation of cellulases, showed increased expression on liquid SB culture. Over 150 potential transporter genes were also identified with increased expression on liquid and semi-solid SB culture. This first comprehensive analysis of the transcriptome of A. tamarii contributes to our understanding of genes and regulatory systems involved in cellulose and hemicellulose degradation in this fungus, offering potential for application in improved enzymatic cocktail development for plant biomass degradation in biorefinery applications.