Enzyme production mechanism of anaerobic fungus Orpinomyces sp. YF3 in yak rumen induced by different carbon source / 生物工程学报

In order to investigate the enzyme production mechanism of yak rumen-derived anaerobic fungus Orpinomyces sp. YF3 under the induction of different carbon sources, anaerobic culture tubes were used for in vitro fermentation. 8 g/L of glucose (Glu), filter paper (Flp) and avicel (Avi) were respectively added to 10 mL of basic culture medium as the sole carbon source. The activity of fiber-degrading enzyme and the concentration of volatile fatty acid in the fermentation liquid were detected, and the enzyme producing mechanism of Orpinomyces sp. YF3 was explored by transcriptomics. It was found that, in glucose-induced fermentation solution, the activities of carboxymethyl cellulase, microcrystalline cellulase, filter paper enzyme, xylanase and the proportion of acetate were significantly increased (P < 0.05), the proportion of propionate, butyrate, isobutyrate were significantly decreased (P < 0.05). The results of transcriptome analysis showed that there were 5 949 differentially expressed genes (DEGs) between the Glu group and the Flp group, 10 970 DEGs between the Glu group and the Avi group, and 6 057 DEGs between the Flp group and the Avi group. It was found that the DEGs associated with fiber degrading enzymes were significantly up-regulated in the Glu group. Gene ontology (GO) function enrichment analysis identified that DEGs were mainly associated with the xylan catabolic process, hemicellulose metabolic process, β-glucan metabolic process, cellulase activity, endo-1,4-β-xylanase activity, cell wall polysaccharide metabolic process, carbohydrate catabolic process, glucan catabolic process and carbohydrate metabolic process. Moreover, the differentially expressed pathways associated with fiber degrading enzymes enriched by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were mainly starch and sucrose metabolic pathways and other glycan degradation pathways. In conclusion, Orpinomyces sp. YF3 with glucose as carbon source substrate significantly increased the activity of cellulose degrading enzyme and the proportion of acetate, decreased the proportion of propionate, butyrate and isobutyrate. Furthermore, the degradation ability and energy utilization efficiency of fungus in the presence of glucose were improved by means of regulating the expression of cellulose degrading enzyme gene and participating in starch and sucrose metabolism pathway, and other glycan degradation pathways, which provides a theoretical basis for the application of Orpinomyces sp. YF3 in practical production and facilitates the application of Orpinomyces sp. YF3 in the future.

Fungos anaeróbios do rúmen de bovinos e caprinos de corte criados em pastagens tropicais / Ruminal anaerobic fungi of beef cattle and beef goats raised on tropical pastures

The presence of anaerobic fungi structures was evaluated in ruminal juice of beef goats and beef cattle raised in the North of Minas Gerais, Brazil. The strains were collected from 18 Anglo-Nubian crossbred male goats and 23 Nellore crossbred steers during the dry period of the year. Physical-chemical characteristics of the juice were evaluated and direct examination with KOH digestion was performed for anaerobic fungi detection. Structures of these fungi were detected in samples of 14 (77.8 percent) goats and 17 (73.9 percent) steers. The monocentric fungi frequency (56.5 percent) was significantly higher in cattle than polycentric fungi frequency (26.1 percent). This study is the first report of anaerobic ruminal fungi in these ruminants in Brazil and showed high prevalence of theses microorganisms in the ruminal ecosystem of both animals.

Screening of Anaerobic Fungi and their Medium Modification for Xylanase Production / 微生物学通报

Twelve anaerobic fungal strains isolated from rumen and faeces of ruminants were screened for xylanase prodution. Isolate A4 strain identified as Neocallimastix had the highest xylanase activity among all isolates. With rice straw, corn straw , peanut straw and filter paper as fermentation substrates, the activities of xylanase by A4 were14.31 U/mL, 11.39 U/mL, 6.99 U/mL, 13.38 U/mL, respectively. The effect of cell-free rumen fluid and yeast extract on xylanase production was tested. The results showed that the concentration level of cell-free rumen fluid had no significant effect on xylanase production. However as yeast extract concentration decreased from 1.0 g/L to 0,5 g/L , the enzyme activity decreased significantly ( P