Fermentation of Apple Pomace Using Mixed Microbial Culture to Organic Acids

The potential of apple pomace (AP) as carbon source for microbial production of biochemicals, via the carboxylate platform, was investigated. The physical and chemical properties of AP were characterized before fermentation by FTIR spectroscopy, TGA, XRD, and compositional (lipids, carbohydrate, lignin and ash) analyses. AP was fermented using a mixed microbial culture (MMC) from wastewater treatment activated sludge. Organic loading (35, 55 and 75 g L-1), temperature (27, 35 and 40°C), gelatinization of feedstock, and a fermentation time of 13 days were examined. The maximum yield of lactic acid was 0.81 g L-1 after 6 days at 35°C and 75 g L-1 feed concentration. However, no significant effect of gelatinization of AP was found to improve fermentation yields. AP fermentation also generated methanol (9.57 g L-1), citric acid (16.8 g L-1), and oxalic acid (24.8 g L-1) with minor amounts of ethanol (0.54 g L-1) and acetic acid (3.42 g L-1). The results of characterization of physical properties, chemical composition and fermentation characteristics of AP waste as source material indicated that AP can be used as potential fermentation substrate using MMC for the synthesis of biochemical products.