In Vitro Cellulase Production from Five Herbivore Microbial Ecosystems and Consortia

Abstract

Abstract As the most abundant biomass in nature, cellulose is the main chemical component in herbivore forages. The energy locked in these complex polymers can only be released by cellulolytic enzymes. Therefore, research aiming to increase the expression of cellulolytic enzymes or browsing uncultured microbial ecosystem in search of potential fibrolytic enzymes is imperative. The main objectives were to: (a) investigate the variation of cellulase enzymes in cow (CW), horse (H), miniature horse (mH), wildebeest (WB) and zebra (ZB); and (b) identify their presence and activeness in microbial consortia, N1 (H+WB), N2 (H+ZB), N3 (WB+ZB) and N4 (H+WB+ZB). Fresh faecal or rumen inocula were cultured in the laboratory on maize stover and lucerne (1:1) with salivary buffer for 72 h at 38°C. Crude proteins (CPZ) were precipitated from both fresh and cultured inocula using 60% ammonium sulfate for enzyme assays and zymography. Endocellulases and their activity were identified on 1% (m/v) carboxymethyl cellulose (CMC) zymograms stained with Congo red. All CPZ extracts were active as reducing sugars were produced after incubation with crystalline cellulose, CMC and xylan. The number and types of proteins with endocellulase activity varied (P<0.05) among and within the different animal species CW (15), H (14), mH (14), WB (13) and ZB (13). Microbial consortia were active with relatively higher number of endocellulases, N1 (17), N3 (14), N4 (14), and N2 (13). Cellulase enzymes vary among and within herbivore species grazing on the same or different fields. Therefore, identifying specific enzymes and microbes with higher fibrolytic potentials from different ecosystems for transinoculation could play a vital role in improving forage digestibility in ruminants