Comprehensive utilization of palm kernel cake for producing mannose and manno-oligosaccharide mixture and yeast culture.

Palm kernel cake (PKC) is an agricultural waste derived from palm kernel oil manufacturing, and its production is increasing year by year. It is very urgent to process this agricultural waste in an environmentally friendly way. Here, PKC was used to produce mannose and manno-oligosaccharides mixture (MMOM) and yeast culture (YC) through enzymolysis and solid-state fermentation (SSF). In enzymolysis, five factors were optimized separately and a response surface methodology analysis was performed. Then, enzymolysis of PKC was carried out at the optimal condition, and the extraction efficiency of mannose and manno-oligosaccharides reached 68.90% with mannose concentration achieving 60.27 g/L. After enzymolysis, the enzymatic hydrolysate was dried by spray drying, and the contents of MMOM reached 42.9%. In SSF, the enzymolysis residues were utilized with inoculating Saccharomyces cerevisiae for yielding YC. After optimization, the cells number of S. cerevisiae reached 2.08 × 109 cells/g and the crude protein content was increased to 27.31%. Therefore, a novel approach to produce feed additives, including MMOM and YC, with high value by comprehensive utilization of PKC was proposed, which has good application prospects in the breeding industry. KEY POINTS: • New idea for the comprehensive utilization of PKC is proposed. • PKC was used to produce mannose and mannan-oligosaccharides mixture (MMOM) by enzymolysis and spray drying. • The enzymolysis residues were reused via SSF for producing yeast culture (YC).