Biomass and Bioenergy 142 (2020) 105752 Available online 19 September 2020 0961-9534/© 2020 Elsevier Ltd. All rights reserved. Research paper Process intensifcation and comparison of bioethanol production from food industry waste (potatoes) by ultrasonic assisted acid hydrolysis and enzymatic hydrolysis: Statistical modelling and optimization T. Suresh a , N. Sivarajasekar a, * , K. Balasubramani b , Tansir Ahamad c, d , Manawwer Alam c , Mu Naushad c, d, ** a Laboratory for Bioremediation Research, Unit Operations Lab, Department of Biotechnology, Kumaraguru College of Technology, Coimbatore 641049, TN, India b Department of Petrochemical Engineering, JCT College of Engineering and Technology, Coimbatore, 641105, TN, India c Department of Chemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia d School of Life and Allied Health Sciences, Glocal University, Saharanpur, India A R T I C L E INFO Keywords: Bioethanol Box-Behnken Neural networks Ultrasonic pretreatment Acidic hydrolysis Enzyme hydrolysis ABSTRACT Biofuel is one of the promising alternatives for petroleum-based fuels and the bioethanol produced from agri- cultural residues/industrial wastes are a viable alternative, and current trend in research. In this context, this work reports the utilisation of the waste potatoes (Solanum tuberosum L.) from food industries as precursors for bioethanol. Waste potato mass (WPM) was pre-treated using ultrasonication and hydrolysed using either hy- drochloric acid (US–HCl) or α-amylase (US-Enzyme). The process conditions such as initial S. cerevisiae con- centration (10–20 g/L), enzyme concentration (10–30 U/mL), HCl concentration (1–3% v/v) and ultra- sonication time (5–15 min) were modelled using Box-Behnken RSM design and artifcial neural networks (ANN). ANN modelled the experimental data better than RSM which was evident from different errors. Optimum parameters were evaluated using genetic algorithm. The optimal parameters predicted for US-HCl hydrolysis was 65.8 mg/L at HCl concentration 2.1%, ultrasonication time 10.7 min, and S. cerevisiae concentration 19.2 g/L with R 2 0.979, whereas, for US-Enzyme hydrolysis was 54.1 g/L at α-amylase concentration 25.3 U/mL, ultra- sonication time 10.2 min, and S. cerevisiae concentration 19.2 g/L with R 2 0.959. Hence, ultrasonic pretreatment increases the bioethanol yield from waste potatoes and US-HCl process was effcient than the US-Enzyme process. 1. Introduction The ever increasing energy demand is met primarily (≈88%) by fossil fuels [1]. However, this energy demand is likely to intensify 26% over the next 20 years due to the rapid growth of industries, automobiles and world population [2]. Hence, there is an alarming concern about future vast energy demands with limited and non-renewable resources [3]. Furthermore, there is an increased awareness on environmental pollu- tion [4], global warming, lascivious usage of fossil fuels and increasing crude oil prices [5]. All of these disturbing factors highlighted the ne- cessity for alternate, viable, profcient, economical, and eco-friendly energy sources to achieve present and future demands [6]. Recent de- cades, researches propelled in the direction of reduction of fossil fuels consumption and release of carbon dioxide [3,7]. A variety of biomasses [7,8] including resources from forest, agricultural, and marine sources have been inspected as precursors for biofuel production. Recent liter- ature [8] pointed out that economically viable biofuel production was achievable through them. Sugarcane, maize, wheat and barley are well known feedstock’s for bioethanol which ultimately challenges the food availability for human beings [9]. Hence, renewable resources such as agricultural and industrial byproducts were examined as feedstock for bioethanol production [10,11]. In this view, food industry wastes and byproducts [10–13] which are abundantly available and inexpensive, have suffcient amounts of hydrolysable starch and fermentable sugars for bioethanol preparation were employed. Particularly, the wastes obtained from potato industries like pulp, processed water, peels, and mash contain good amounts of starch [12]. Solanum tuberosum L. is a crop grown for its starchy tuberous * Corresponding author. ** Corresponding author. E-mail addresses: sivarajasekar@gmail.com (N. Sivarajasekar), mnaushad@ksu.edu.sa (M. Naushad). Contents lists available at ScienceDirect Biomass and Bioenergy journal homepage: http://www.elsevier.com/locate/biombioe https://doi.org/10.1016/j.biombioe.2020.105752 Received 3 May 2020; Received in revised form 11 August 2020; Accepted 24 August 2020