Effect of pretreatment techniques on enzymatic hydrolysis of food waste

Food waste could be acknowledged as an auspicious feedstock for bioethanol production, given its high organic and polysaccharides' content. In an effort to render enzymatic hydrolysis of food waste more efficient and maximize sugar release, six different thermal, sono-electrochemical, and chemical pretreatment methods were examined. In all cases, starch was solubilized from 26.8 to 42.8% releasing from 1.38 to 2.14 g glucose per 100 g food waste. After 6 h of enzymatic saccharification, the glucose yield was higher than the respective value of the control trial (no pretreatment) for all the experiments, apart from the hydrolysates from thermal autoclaving, implying the presence of possible inhibitory compounds. Saccharification yields ranging 16.43-17.31 g glucose per 100 g raw material after sono-electrochemical pretreatments were not significantly improved and thus if other techno-economic factors are also taken into account, their application may not stand as a viable option. The highest glucose concentrations were observed in food waste hydrolysates that had been subjected to oil extraction with hexane, with 21.66 g glucose per 100 g raw material and 90.30% and 53.75% starch and cellulose degradations, respectively. Thus, oil extraction was qualified as an appropriate pretreatment for food waste, as high glucose yield and starch and cellulose degradations were obtained after enzymatic hydrolysis.