Improvement of bioethanol production from waste chestnut shells via evaluation of mass balance-based pretreatment and glucose recovery process

Chestnut shells (CSs) are a high-carbohydrate food waste generated by bioindustries. These are gaining popularity as promising biorefinery resources. In this study, we optimized the potassium hydroxide (KOH) pretreatment conditions for CS using response surface methodology in order to efficiently recover glucose via enzymatic saccharifica-tion. Here, biomass to glucose conversion (BtGC) was set as the response value, and the optimal conditions for maximum BtGC were determined using a prediction model in the following manner: CS loading, 92.7 g/L; temperature, 38.6 degrees C; time, 2.5 h. In the predictions and experiments, BtGC was 15.3% and 15.7% (glucan content: 69.1%, enzymatic digestibility [ED]: 39.7%, and solid recovery: 51.9%), respectively, a 2.5-fold improvement compared to the control group (6.3%). A profiling experiment was also performed to determine appropriate enzyme loading, resulting in an ED of 75.7%. Finally, CS hydrolysates were utilized as a medium for Saccharomyces cerevisiae K35 and had no inhibitory effect during fermentation. Finally, bioethanol production was estimated to be 150 g based on a mass balance of 1000 g CS. This study points in the right direction for achieving a sustainable society by valorizing food waste for biofuel production.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this study, the potassium hydroxide (KOH) pretreatment conditions for chestnut shells (CSs) were optimized to efficiently recover glucose. The biomass to glucose conversion (BtGC) was significantly improved by 2.5-fold using enzymatic saccharification. Additionally, the CS hydrolysates showed no inhibitory effect on Saccharomyces cerevisiae fermentation, indicating the potential for bioethanol production.