Screening and evaluation of cellulytic fungal strains for saccharification and bioethanol production from rice residue Shiv Prasad a , Sandeep Kumar a , Krishna Kumar Yadav b, * , Jairam Choudhry c , Hesam Kamyab d , Quang-Vu Bach e, ** , K.R. Sheetal f , Sudha Kannojiya a , Neha Gupta b a Centre for Environment Science and Climate Resilient Agriculture, Indian Agricultural Research Institute, New Delhi,110012, India b Institute of Environment and Development Studies, Bundelkhand University, Kanpur Road, Jhansi, 284128, India c Indian Institute of Farming Systems Research, Modipuram, Meerut, 250110, India d Department of Engineering, UTM Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, Malaysia e Institute of Research and Development, Duy Tan University, Danang, 550000, Viet Nam f ICAR-Central Arid Zone Research Institute, Regional Research Station, Bikaner, Rajasthan, 334004, India article info Article history: Received 28 June 2019 Received in revised form 30 September 2019 Accepted 22 October 2019 Available online 25 October 2019 Keywords: Rice straw Bioethanol Pretreatment Saccharification Fermentation abstract In this study, microwave-assisted alkali and acid pretreated rice straw were used to improve fermentable sugar yield by enzymatic saccharification (ES) employing cellulolytic fungal strains and subsequent bioethanol production by using fermenting yeast. The cellulolytic fungal strains Trichoderma reesei NCIM 1052, 1186, 992, T. reesei ITCC 4025, 6413, Aspergillus niger ITCC 302, A. acculeatus ITCC 5078, A. fumigates ITCC 4768 and Fusarium Solani ITCC 6397 were used for enzymatic saccharification (ES) of acid/alkali pretreated rice straw to optimize the sugar recovery. T. reesei NCIM 1052 was found superior as compared to the other fungal strains in terms of FPase, CMCase activities, and reducing sugars yield from pretreated rice straw. The strains of Saccharomyces cerevisiae NCIM 3186, and Pichia stipitis NCIM 3499 were used for subsequent fermentation to produce bioethanol. The saccharification of alkali pretreated rice straw (2% v/ w NaOH) by T. reesei NCIM 1052 resulted in the highest fermentable sugar yield (55.6 g/l) and ultimately, the higher ethanol concentration after 72 h of fermentation with P. stipitis NCIM 3499 (25.3 g/L) as compared to other yeast strains. This study also exhibits the high potential for economic generation of ethanol from rice straw. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Energy is most crucial for the socio-economic development of a nation. Fluctuation in the prices of crude oil severely affects the economics of the country, especially of developing countries like India. Since energy is mainly conventional fossil fuel-driven, which are limited, non-renewable resources. Therefore, researchers have to explore renewable sources of energy to meet demand world- wide. Previously, the maximum study has pointed to concentrate on producing an economical and eco-friendly bioethanol produc- tion means [1]. Currently, in vehicles, blended ethanol is used as an alternative fuel to raise the octane number and enhance fuel efficiency [2,3], also reducing CO 2 emission [4]. Though, bioethanol generation from agricultural and food crops such as maize, potato, and sugarcane (1st generation biofuels) has resulted in an un- wanted direct conflict with the food supply and distribution [5]. A switch to a more plentiful non-edible crop matter should help to lessen the burden on the food crops. Therefore, with a remarkable production estimated at 1  10 10 MT per annum worldwide [6], lignocellulosic biomass is considered as the only foreseeable, sus- tainable, feasible and renewable source of energy and value-added chemicals [7]. Consequently, the major emphasis is being given on lignocel- lulosic biomass, a viable feedstock for ethanol generation by the microbial fermentation [8]. In the past, farmers burned rice straw as the most common economical method of management. Presently, the burning of crop residues in the open field is a significant concern as it is creating several health issues [1 ,9]. Residue burning also contributes to global warming and have a negative impact on soil health. Now, agro-residues based energy generation is * Corresponding author. ** Corresponding author. Institute of Research and Development, Duy Tan Uni- versity, Danang, 550000, Viet Nam. E-mail addresses: envirokrishna@gmail.com (K.K. Yadav), bachquangvu@ duytan.edu.vn (Q.-V. Bach). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy https://doi.org/10.1016/j.energy.2019.116422 0360-5442/© 2019 Elsevier Ltd. All rights reserved. Energy 190 (2020) 116422