Modelling the effect of cellulase loading and substrate concentration on enzymatic saccharification of Indian mango (Mangifera indica) peelings for bioethanol production

Abstract

The main objective of the study was to develop a mathematical model to show the effect of cellulase loading and substrate concentration on the reducing sugar during enzymatic saccharification of Indian mango peelings for bioethanol production. This investigation also determined the effect of three pretreatment methods namely: dilute acid, dilute alkaline, and dilute alkaline peroxide pretreatment on the properties if powdered unripe Indian mango peelings. Likewise, the effect of the variation of two saccharification parameters - enzyme loading and substrate concentration on the reducing sugar - was sought

The powdered dried unripe mango peel was subjected to three pretreatment methods: dilute acid using 0.8M H₂SO₄ solution, dilute alkaline using 1M NaOH solution, and dilute alkaline peroxide (2%) pretreatment. The properties of the peels were compared before and after treatment. During enzymatic saccharification, varying substrate concentration- 3 g/mL, 4 g/mL, and 5 g/mL of mango peelings were used and varying enzyme loading10 mL, 15 mL, and 20 mL of cellulase enzyme were used to determine the effect of such variation in the reducing sugar concentration. Using the obtained values of reducing sugar at varying cellulase loading and substrate concentration as input data in the Minitab 16 software, the RSM Regression Model equation was developed.

The study revealed that dilute sodium alkaline pretreatment significantly decreased the lignin content of Indian mango peels. The optimal saccharification condition of Indian mango peel were identified at 20 mL of cellulase and 3 g/mL of substrate. Using Response Surface Methodology (RSM) via Regression, a mathematical model was developed in order to determine the optimum saccharification condition in terms of cellulase loading and substrate concentration, and their effect on the reducing sugar concentration.

Dilute acid pretreatment has the greatest effect in increasing reducing sugar and starch, while dilute alkaline pretreatment has the greatest effect in increasing the lignocellulosic properties of Indian mango peelings and likewise caused greatest delignification of the sample. The percent reducing sugar after enzymatic saccharification implied that at lower substrate concentration and higher cellulase loading, a greater amount of reducing sugar concentration can be achieved. The mathematical model generated explains the effects of substrate concentration and enzyme loading on the reducing sugar concentration.