Protein enrichment, cellulase production and in vitro digestion improvement of pangolagrass with solid state fermentation

Background and PurposePangolagrass, Digitaria decumbens Stent, is a major grass for cow feeding, and may be a good substrate for protein enrichment. To improve the quality of pangolagrass for animal feeding, cellulolytic microbes were isolated from various sources and cultivated with solid state fermentation to enhance the protein content, cellulase production and in vitro digestion. The microbes, culture conditions and culture media were studied.MethodsCellulolytic microbes were isolated from pangolagrass and its extracts, and composts. Pangolagrass supplemented with nitrogen and minerals was used to cultivate the cellulolytic microbes with solid state fermentation. The optimal conditions for protein enrichment and cellulase activity were pangolagrass substrate at initial moisture 65–70%, initial pH 6.0–8.0, supplementation with 2.5% (NH4)2SO4, 2.5% KH2PO4 and K2HPO4 mixture (2:1, w/w) and 0.3% MgSO4.7H2O and cultivated at 30oC for 6 days.ResultsThe protein content of fermented pangolagrass increased from 5.97–6.28% to 7.09–16.96% and the in vitro digestion improved from 4.11–4.38% to 6.08–19.89% with the inoculation of cellulolytic microbes by solid state fermentation. Each 1 g of dried substrate yielded Avicelase 0.93–3.76 U, carboxymethylcellulase 1.39–4.98 U and β-glucosidase 1.20–6.01 U. The isolate Myceliophthora lutea CL3 was the strain found to be the best at improving the quality of pangolagrass for animal feeding with solid state fermentation.ConclusionSolid state fermentation of pangolagrass inoculated with appropriate microbes is a feasible process to enrich protein content, increase in vitro digestibility and improve the quality for animal feeding.