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

Background and Purpose

Pangolagrass, 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.

Methods

Cellulolytic 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 30^oC for 6 days.

Results

The 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.

Conclusion

Solid 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.

Keywords: Cellulase production, In vitro digestion, Pangolagrass, Protein enrichment, Solid state fermentation