Send Orders for Reprints to reprints@benthamscience.net Current Biochemical Engineering, 2020, 6, 000-000 1 RESEARCH ARTICLE 2212-7119/20 $65.00+.00 © 2020 Bentham Science Publishers Effect of Choline Acetate on the Yeast Cells During Fermentation: Kinetics Approach Amal A. Elgharbawy 1,* , Md. Zahangir. Alam 2 , Muhammad Moniruzzaman 3 , Nassereldeen Ahmad Kabbashi 2 , Parveen Jamal 2 and Shiva Rezaei Motlagh 4 1 International Institute for Halal Research and Training (INHART), International Islamic University Malaysia, PO Box 10, Kuala Lumpur 50728, Malaysia; 2 Department of Biotechnology Engineering, Kulliyyah of Engineering, Internation- al Islamic University Malaysia, PO Box 10, Kuala Lumpur 50728, Malaysia; 3 Chemical Engineering Department, Cen- tre of Research in Ionic Liquids (CORIL), Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Malaysia; 4 Department of Chemical and Environmental Engineering, Faculty of Engineering, University Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia Abstract: Background: Ionic liquids (ILs) are claimed as green solvents and have demonstrated abil- ity in the dissolution of several biomaterials and polymers, thus promoting their applications in wide scope. The aim of this study was to evaluate the yeast cells in the ionic liquid (IL), choline acetate [Cho]OAc as an eco-friendlier IL for their growth and ability of fermentation of the empty fruit bunch (EFB) biomass for ethanol production via monitoring the cell growth curve and kinetics. Methods: The Saccharomyces cerevisiae was cultured for five days on yeast extract-peptone-dextrose (YPD) agar and the sub-culturing was carried out every two weeks to evaluate the growth of yeast in [Cho]OAc at different concentrations; 5%, 10%, and 20%, where it was pre-cultivated for 24 h at 30 °C and 150 rpm in a shaking incubator as a control culture. Yeast cell number was determined by counting using a hemocytometer. Also, the kinetic growth of yeast during the fermentation of EFB was evaluated. Result: cell concentration increased, ethanol production increased along with the optical density with the peak reached at 72 h, then declined. Enzymatic hydrolysis process followed by fermentation of EFB using [Cho][OAc] improved the yield of sugar, saccharification and ethanol around 1.938, 2.879, and 2.165 times in comparison with untreated EFB with IL. Furthermore, values of specific growth rates obtained in IL-medium and non-IL-medium are applicable for ethanol production to take place. The results showed the ability of yeast cells for fermentation even in the presence of IL. Conclusion: The results showed that the presence of the IL did not suppress the growth of the yeast cells and did not impair the fermentation productivity. A R T I C L E H I S T O R Y Received: April 16, 2020 Revised: July 01, 2020 Accepted: July 22, 2020 DOI: 10.2174/2212711906999200816125102 Keywords: Ionic liquids, fermentation, hydrolysis, cellulase, kinetics, growth curve. 1. INTRODUCTION Ionic liquids (ILs), which are regarded as “green sol- vents,” have attractive properties, including their ability to dissolve complex carbohydrates and other biomaterials and polymers. ILs are salts in a liquid state and typically have melting points below 100 °C. As such, these compounds possess characteristics that make them attractive for a broad range of applications. While costly to purchase or produce in the laboratory, their overall performance and prolonged re- use-ability allow for the costs associated with the initial *Address correspondence to this author at the International Institute for Halal Research and Training (INHART), International Islamic University Malaysia, PO Box 10, Kuala Lumpur 50728, Malaysia; Tel: 0162464208; E-mails: amalgh@iium.edu.my; amal.elgharbawy@gmail.com capital expenditure to be offset over time [1]. Some ILs have been used in many applications as clean solvents as green process catalysts, as well as in photochemistry and electro- synthesis. Because of the adaptable properties of ILs, en- zymes exhibit enhanced activity or stability in the presence of some ILs [2] An IL containing an appropriate combination of the cationic and anionic parts might considerably increase substrate specificity, improve the selectivity, or enhance the bioprocess in concern [3, 4]. To date, presenting ILs into many industrial processes has enhanced productivity, yield, and provides an additional benefit of reuse and recyclability [5, 6]. The expanding popularity of ILs and the recent pro- duction on a large scale due to their possible applications could lead to their release uncontrollably into the environ- ment. Therefore, more safety details and concerns should be addressed in order to presume the green and clean prospect