Evaluation of the acidogenic fermentation potential of food industry by-products

Food industry annually generates huge amounts of waste and by-products, whichrepresent untapped renewable resources to produce platform chemicals (e.g., organicacids) through biological processes, such as acidogenic fermentation (AF). Here, the AFpotential of nine food industry by-products has been evaluated in anaerobic batchexperiments, with main attention to the spectrum of attained products and relatedconversion yields. Farinaceous by-products, especially Bread Crust (BC) and RegroundPasta (RP), exhibited the highest conversion yield of the initial Chemical Oxygen Demand(COD) into AF products, up to values of 55 ± 2% and 75 ± 9% (for BC and RP,respectively). Substantially lower values, ranging between 6 ± 1% (for Spinach, SP) and22 ± 1% (for Grape pomace Lees, GL) were achieved with by-products from the vegetableand winery industry. Further experiments with GL, SP, and WP (White exhausted grapePomace) in the presence of glucose as reference substrate, revealed the coexistence ofboth recalcitrant and inhibitory compounds in GL and WP, whereas no inhibition onmicrobial activity was displayed by SP. A sonication pre-treatment experiment (at a lowfrequency of 20 kHz for 15 minutes and at room temperature) allowed increasing theconversion yield of GL by approximately 45%.