Simultaneous enzymatic hydrolysis and bioconversion of deacetylated and disk refined sugarcane bagasse to single-cell protein: An experimental investigation and techno-economic analysis

Abstract

Rising animal feed costs are driving up animal agriculture and food prices. While single-cell protein (SCP) production from lignocellulosic waste offers a solution, pretreatment of these feedstocks is required. In this study, the SCP yield from sugarcane bagasse pretreated via deacetylation in combination with disk refining (DDR), prior to simultaneous enzymatic hydrolysis and fermentation using P. ostreatus and F. venenatum compared to S. cerevisiae, was investigated. A biorefinery was simulated to investigate the economic feasibility of animal feed enhanced with SCP, using a discounted cashflow analysis. Deacetylation and DDR were effective pretreatment approaches, improving enzymatic digestibility from 9.10 g sugar/100 g dry matter (DM) to 75.75 and 80.14 g sugar/100 g DM, respectively, which was comparable to steam-explosion pretreatment. Pretreated bagasse was successfully converted to SCP through simultaneous enzymatic hydrolysis and bioconversion. However, DDR was preferred for bioconversions using P. ostreatus and F. venenatum, achieving SCP yields of 4.24 ± 0.17 and 3.47 ± 0.33 g protein/100 g DM, respectively. In the ranges investigated, solids loading had a more pronounced effect on the SCP yield than enzyme dosage, irrespective of the microorganism used. However, the minimum selling price of animal feed enhanced with SCP (0.69 US$/kg) remains higher than the market price of animal feeds like soybean meal (0.40 US$/kg). The technology shows promise but can be further optimised.