Production of single-cell protein by Candida Utilis and Komagataella Pastoris from enzymatically hydrolyzed defatted soybean meal

Abstract

Defatted soybean meal (D-SBM), a byproduct of soybean oil production, offers high protein content but is limited in its effectiveness as feed to non-ruminant animals due to its indigestible carbohydrate fractions. This study investigates the performance of enzymatic hydrolysis of D-SBM to convert its carbohydrates into monomeric sugars, followed by their utilization as a carbon source to produce single-cell protein (SCP) using Candida utilis and Komagataella pastoris. Optimized enzymatic hydrolysis with 22 mg protein·g⁻¹ D-SBM of total enzyme loading achieved a total monomeric sugar yield of 33.0 ± 1.6 %. Cell propagation experiments demonstrated that K. pastoris and C. utilis utilized enzymatic hydrolysis-derived hexoses, namely glucose, as carbon sources. Both yeasts reached maximum growth rates between 2 and 8 h of cultivation, reaching maximum specific growth rates of 0.268 h⁻¹ and 0.177 h⁻¹, respectively. Single cell production was efficient, with yields of approximately 1.3 g protein·g⁻¹ of monomeric sugar consumed, resulting in SCP contents of approximately 41 % from both yeasts. Amino acid analysis revealed a significant improvement in lysine and methionine levels of 67 % and 52 %, respectively, in crude protein from K. pastoris relative to D-SBM.

This study highlights the potential of D-SBM as a sustainable feedstock for SCP production, providing an innovative approach to repurpose agricultural feedstocks into nutritionally higher quality protein. This transformation can potentially contribute to the development of cost-effective and environmentally friendly alternatives to conventional animal protein sources.