Process Safety and Environmental Protection 128 (2019) 203–210 Contents lists available at ScienceDirect Process Safety and Environmental Protection journal homepage: www.elsevier.com/locate/psep Direct conversion of fruit waste to ethanol using marine bacterial strain Citrobacter sp. E4 Debapriya Sarkar, Kriti Gupta, Kasturi Poddar, Rimi Biswas, Angana Sarkar ∗ Department of Biotechnology and Medical Engineering, National Institute of Technology Rourkela, Odisha, 769008, India a r t i c l e i n f o Article history: Received 3 April 2019 Received in revised form 24 May 2019 Accepted 26 May 2019 Available online 31 May 2019 Keywords: Waste Ethanol Fermentation Marine bacteria Optimization Scale-up a b s t r a c t Ethanol tolerant strains were isolated from the marine waters of Digha and Shankarpur of West Ben- gal, India and screened for ethanol production using several domestic wastes including, paper, kitchen, garden, and fruit wastes. Strain E4 was found to be the most efficient in ethanol production through fermentation of kitchen and fruit waste. Phylogenetic analysis of the 16S rRNA gene of strain E4 showed its closeness to Citrobacter sp. Production of 2.96 g/l of ethanol was obtained using fruit waste using High- Performance Liquid Chromatography (HPLC) analysis. The yield of ethanol production was obtained as 0.13 g of ethanol/g of reducing sugar present in fruit waste. Although after optimization of fermentation condition, the yield was improved to 0.30 in batch scale. The production was optimized using Central Composite Design. The production was scaled up to 4 l culture volume in the stirred tank bioreactor. Finally, a distillation of fermentation broth resulted in 16.10 ml of product with a yield of 0.30 g of ethanol from 1 g of fruit waste. Thus the isolated marine strain Citrobacter sp. E4 could be potentially used for ethanol production from fruit wastes without any pretreatment in a cost-effective and eco-friendly way. © 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Large scale and overutilization of fuels have posed a serious threat to our natural, exhaustible, and combustible non-renewable energy reserves. With the budding human population and their increased use of industrial productivity, the global energy con- sumption has also notably accelerated causing a decline in the net global production of oil. This scenario encourages us to con- sider renewable resources as an alternative source of energy. In the recent past, the global ethanol production has been reported to be more than 1.2 billion of ethanol (both fuel and non-fuel)/year (Licht, 2018). However, the market demand for ethanol in India has been reported to have increased up to almost 20 Mbbl/day until 2016 (Popps, 2018). Though the combustion of ethanol produces carbon dioxide, however, the amount of greenhouse gas emission is comparatively less than that of non-renewable fossil fuels, thus leaving behind less harmful impacts on the environment. Hence, to support the emerging demand globally, bio-ethanol production has become a concern worldwide. ∗ Corresponding author. E-mail addresses: deb.apn@gmail.com (D. Sarkar), k.gpt29@gmail.com (K. Gupta), kasturi.p93@gmail.com (K. Poddar), rimi.biswas12@gmail.com (R. Biswas), sarkara@nitrkl.ac.in (A. Sarkar). Previously ethanol has been produced by chemical methods as well as through conventional methods, like fermentation. The chemical process includes the reaction of ethylene with steam under high temperature and high pressure. Although this process is faster than fermentation, however, fermentation is advantageous in terms of utilization of renewable crops and less hi-tech infras- tructure requirement (Gnansounou and Dauriat, 2005). Bio-ethanol has already been produced in the last few decades through vari- ous conventional methods. The first generation of bio-ethanol was produced using food crops like, sugarcane and grains which led to food crop scarcity and subsequent rise in crop cost. Simultane- ously, the availability of enough fertile land and cheap labor was also a problem (Elshahed, 2010). This drove to the development of the second generation bio-ethanol production using woody solid biomass, energy crops, other agricultural, forestry products, and solid wastes (Mohr and Raman, 2013). However, it prompted neg- ative production issues like energy-intensive process, high cost and the release of huge carbon dioxide from the processes and hydrolysis of cellulosic materials, physicochemical, and enzymatic treatments, giving rise to environmental contamination (Nair et al., 2016; Robak and Balcerek, 2018). Thereafter, researchers are work- ing towards the third generation bio-ethanol production from algal biomass. Ethanol is a renewable energy source producible from sugar fermentation, agricultural livestock, and microorganisms. https://doi.org/10.1016/j.psep.2019.05.051 0957-5820/© 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.