From wheat straw to soluble yeast extract: enhanced mycoprotein production by adaptively evolved Trichosporon cutaneum and fermentation pH shifting.

Single-cell protein (SCP) produced by yeast using low-cost agricultural wastes shows great potential as an alternative protein source for animal and human nutrition. In this study, we developed an adaptive evolution method coupled with centrifugal fractionation and pH shifting to enhance SCP production by Trichosporon cutaneum from wheat straw. During the adaptive evolution, the culture pH was shifted from 5.0 to 7.0, which is more favorable for SCP accumulation of T. cutaneum. The finally obtained T. cutaneum CL160 exhibited a 109.2% increase in SCP content compared to the parental strain. The DCW and SCP titer of T. cutaneum CL160 reached 48.6 ± 1.5 g/L and 14.2 ± 1.1 g/L using wheat straw clarified hydrolysate by batch fermentation. Fed-batch fermentation using wheat straw-derived syrup further improved DCW and SCP titer to 124.2 g/L and 32.6 g/L. Further attempts were performed to prepare soluble yeast extract from lignocellulose-derived SCP by cell autolysis. This yeast extract served as an effective nitrogen source for lactic acid fermentation by Pediococcus acidilactici, achieving 83.2 ± 1.1 g/L lactic acid titer and 45 × 10⁹/mL CFU value, comparable to commercial yeast extract. This study demonstrates the conversion of waste lignocellulosic feedstocks into sustainable SCP and soluble yeast extract, presenting an innovative strategy for the valorization of non-food lignocellulosic feedstocks.