OPTIMISATION OF MICROWAVE PRETREATMENT CONDITIONS OF ORANGE AND PLANTAIN PEELS FOR POLYGALACTURONASE PRODUCTION BY ASPERGILLUS AWAMORI CICC 2040

Abstract

This study investigated the optimisation of microwave pretreatment of orange and plantain peels for polygalacturonase (PG) production, by Aspergillus awamori CICC 2040, using response surface methodology. The microwave pretreatment factors interacted were particle size (PS) (<0.4250, 0.4250<PS<0.8025, and 0.8025<PS<1.1800 mm), microwave power (240, 480 and 720 W) and time (2.50, 6.25, and 10.00 min.). These factors were interacted to determine combinations for maximum polygalacturonase activity (MPA). Pretreated orange and plantain peel powders were inoculated with 106 spores/mL Aspergillus awamori CICC 2040, incubated at 28oC for 5 days, and crude polygalacturonase was extracted and its activity determined. Same microwave pretreatment combination, 0.8025<PS<1.1800 mm, 720 W and 10.00 min, gave MPA for orange and plantain peels. The MPA from orange and plantain peels was 26.21 and 26.72 U/mL, respectively. F and p values obtained for orange peel powder were 35.42 and 0.00, respectively while those obtained for plantain peel powder were 5.71 and 0.006, respectively. R2 and R2 (adjusted) of 96.96 and 94.22%, respectively were obtained for PG activity produced using orange peel powder while 90.71 and 79.04% were recorded for PG activity produced using plantain peel powder. Optimised microwave pretreatment conditions of orange and plantain peels for MPA from Aspergillus awamori CICC 2040 were established. Keywords: Aspergillus awamori, Fruit peel, Microwave, Optimisation, Polygalacturonase, Pretreatment,