Hydrodynamic cavitation assisted pretreatment of sugarcane bagasse in the presence of yeast cell mass for the production of sugars and their use for biopigments production by Monascus ruber

Abstract

Hydrodynamic cavitation-assisted pretreatment of sugarcane bagasse tested in the, with the addition of yeast extract. This pretreatment was investigated using a 22 central composite design experiment. A total of 11 experiments were performed. The pretreated biomass was then tested for enzymatic hydrolysis for the sugars production. Various enzymatic loadings (15–20 FPU/g biomass) and concentrations of yeast extract (0.25–1 g/L) were studied during the enzymatic hydrolysis. Optimization of yeast extract insertion was performed to simultaneously facilitate the infusion of cellulolytic enzymes into the pores of the pre-treated bagasse concomitantly inhibiting enzyme absorption caused by residual lignin. The optimized results revealed an 81 % glucan hydrolysis yield and a 78 % xylan hydrolysis yield after the enzymatic hydrolysis under optimized conditions (20 FPU/g and 1 g/L of yeast extract). The hydrolysate rich in sugars derived from carbohydrate polymers and nitrogen sources derived from hydrolysis of yeast cream was assessed for biopigments production by Monascus ruber. The hydrolysate used for M. ruber fermentation showed the production of pigments with 15 AU (absorbance units) for yellow, 15 AU for orange and 20 AU for red after 9 days of fermentation. These results proved the efficiency of using yeast cream as a potential blocking agent of lignin in turn increasing the sugars production and a nitrogen source for the M. ruber for biopigments production from sugarcane bagasse hydrolysate.