Sustainability analysis of orange peel biorefineries

Production of mannooligosaccharides from orange peel waste with β-mannanase expressed in Trichosporonoides oedocephalis

A large quantity of orange peel waste (OPW) is generated per year, yet effective biorefinery methods are lacking. In this study, Trichosporonoides oedocephalis ATCC 16958 was employed for hydrolyzing OPW to produce soluble sugars. Glycosyl hydrolases from Paenibacillussp.LLZ1 which can hydrolyze cellulose and hemicellulose were mined and characterized, with the highest β-mannanase activity of 39.1 U/mg at pH 6.0 and 50 ℃. The enzyme was overexpressed in T. oedocephalis and the sugar production was enhanced by 16 %. The accumulated sugar contains 57 % value-added mannooligosaccharides by the hydrolysis of mannans. The process was intensified by a pretreatment combining H2O2 submergence and steam explosion to remove potential inhibitors. The mannooligosaccharides yield of 6.5 g/L was achieved in flask conversion and increased to 9.7 g/L in a 5-L fermenter. This study improved the effectiveness of orange peel waste processing, and provided a hydrolysis-based methodology for the utilization of fruit wastes.