Substantial physicochemical pretreatment and rapid delignification of lignocellulosic banana, pineapple and papaya fruit peels: A study on physical-chemical characterization

Lignocellulosic biomass is a promising precursor for producing various value-added products. The present study examines the potentiality of yellow banana peel (YBP), pineapple peel (PAP), and papaya peel (PP) as substrates for producing reducing sugar. The primary characterization studies were performed using XRD, FTIR, proximate, ultimate and fibre analysis. Results indicate that banana peels are more fibrous and have greater hemicellulose susceptibility (19.55 +/- 0.488 wt%) than other peels (15.4 +/- 0.38 and 15.9 +/- 0.39 wt%). Pretreatment investigations were conducted utilizing various parameters of physical (hot water and microwave hot water) and chemical (acid and alkali) techniques. The findings suggest that higher delignification was found for alkali at 0.03 M ammonia (81.1%) and microwave at 545 W (34.4%). Based on the individual higher performance, the study hypothesizes to combine microwave and ammonia as microwave-ammonia pretreatment (MAP) to enhance the reducing sugar. As a result, 0.03 Mammonia and 545W for 2 min of MAP delignified the banana (94.5%), pineapple (90%), and papaya (80.4%), respectively. The main mechanism involved in the processes is the electromagnetic waves disrupts heterogeneous structures through dielectric polarization which stimulates the enzymatic hydrolysis with short duration to produce more reducing sugars.. The MAP with cellulase (MAPC) was enzymatically hydrolyzed using Cellic (R) CTec2 at 25FPU/g for 48hrs to improve the higher reducing sugar content of bananas (168 mg/g substrate), pineapples (160 mg/g sub-strate), and papayas (145 mg/g substrate). The study found that the combined pretreatment interrupts the cellulose microfibril glycosidic linkages which increaseses hexose releasethat could potentially be used for producing viable products.