Effect of pretreatments on physicochemical Characteristics of Olive Pomace and on Production of cellulases from trichoderma reesei RUT C30 under solid-state fermentation

Abstract

Olive pomace (OP) is a cheap and abundant agricultural by-product that could be valorized by different biotechnological processes. The present study was conducted to better understand the effects of alkaline, milling and thermal pretreatments on OP for obtaining high value-added products (cellulases). Trichoderma reesei RUT C-30 fungus was used for cellulases production on OP substrate under Solid-State Fermentation (SSF) process and cellulases activity was assessed by the filter paper method (FPase). The effect of the three pretreatments and their combinations on physico-chemical composition and cellulases production was investigated. Results showed that untreated OP was a favorable environment for the growth of T. reesei and a good fermentation substrate that gave FPase activity of 0.83 IU/g DS. The chemical composition (lipids, proteins, carbohydrates and ash) was significantly (P < 0.05) affected by the different pretreatments as well as their combinations. Regarding the fiber fraction, alkaline and thermal pretreatments did not affect the NDF content, while a remarkable decrease (29.88%) was recorded after milling pretreatment. Alkaline pretreatment decreased significantly the cellulose contents whereas milling increased it of 35%. ADL fraction was only decreased by the milling treatment of 42%. No significant effect of thermal pretreatment was noticed on ADL and cellulose. The alkaline pretreatment with 1% NaOH improved the cellulase activity to a value of 1.28 IU/g DS, while lower yields were obtained after milling (0.2 IU/g DS) and thermal (0.15 IU/g DS) pretreatments. This study showed that only alkaline treatment improved the production of cellulase from OP without being combined with milling and thermal treatment