~ 2023 ~ International Journal of Chemical Studies 2018; 6(5): 2023-2027 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2018; 6(5): 2023-2027 © 2018 IJCS Received: 14-07-2018 Accepted: 18-08-2018 Sugandha Mahajan Department of Microbiology, Punjab Agricultural University, Ludhiana, Punjab, India Gurvinder Singh Kocher Department of Microbiology, Punjab Agricultural University, Ludhiana, Punjab, India Correspondence Sugandha Mahajan Department of Microbiology, Punjab Agricultural University, Ludhiana, Punjab, India Standardization of sugar beet juice extraction by microwave heating and its fermentation for bioethanol production Sugandha Mahajan and Gurvinder Singh Kocher Abstract Sugar beet juice was used as a substrate for bioethanol production owing to its high sucrose content as an alternative to first generation sucrose resources such as molasses, sugar cane juice etc. The juice of sugar beet, variety SZ-35, was extracted by microwave pre-heating treatment of succulents for 10 minutes giving total soluble solids (12.8 ± 0.74 ˚B). Two yeast strains, Saccharomyces cerevisiae KY069279 (isolated strain) and Saccharomyces cerevisiae D7 (commercial strain), were studied for their growth profile on sugar beet juice which revealed Saccharomyces cerevisiae KY069279 to have maximum growth rate (0.45 per hour) at 12 hours of shaking conditions. The selected yeast strain Saccharomyces cerevisiae KY069279 was further employed for the optimization of fermentation parameters (brix, inoculum size (%v/v) and DAHP supplementation (mg/100ml)) using RSM plan of Design Expert 10.0 software. The results were recorded in three responses viz. brix, reducing sugars and ethanol revealed 14.5˚B with inoculum size of 6%v/v, supplemented with 1mg/ml of DAHP was found to produce maximum ethanol (8.61%v/v) after 92 hours of fermentation at 25˚C with a fermentation efficiency of 92.7%. Keywords: bioethanol, fermentation, microwave, Saccharomyces cerevisiae yeast, sugar beet Introduction Bioethanol is produced by fermenting carbohydrates present in the sugar or starchy crops. Currently, modern industrial bioethanol generation plants utilize juice or molasses from sugar crops and starch from cereal crops as their substrates. However, molasses possess alternate uses as source of industrial ethanol, potable ethanol and supplement in animal feed and are thus insufficient for meeting complete demand of bioethanol in the country. Hence, there is need to search for alternate first generation substrates that don’t have food-fuel debate and can be easily fermented. Among such different energy crops sugar beet, sweet sorghum, fruit waste are few names that are potential candidates. Sugar beet has an immense endurance to a broad range of climatic deviations and the water and fertilizer requirement of the crop is 30-40% less in comparison with sugar cane whereas sugar content is almost comparable to that of sugarcane (Chakauya et al 2009) [13] . Biochemically, sugar beet contains enough amounts of sucrose (16 - 20%) like in sugarcane as it can be readily fermented by Saccharomyces cerevisiae. Direct processing of sugar beets in fermentation, without first having to go through sugar extraction and refinery, potentially lowers feedstock related costs for fermentative products. However, sucrose is present in its bound state in sugar beet causing its extraction a rate limiting step that involves pre-treatment processes such as diffuser, osmosis etc. The pre- treatment provided is relatively mild in comparison to that of enzymatic hydrolysis in case of starch and lignocellulosics. According to Berlowska et al (2017) [2] , the medium obtained after enzymatic hydrolysis is a source of carbohydrates that can be metabolized by ethanol- synthesizing yeast to produce ethanol. Sugar beet molasses has also been earlier used as a feedstock for ethanol production (Dodic et al 2009) [5, 11] . The highest ethanol yield reported by Marx et al (2012) [8] for sugar beet was 0.49 g/g which corresponds to a fermentation efficiency of 96%. Sugar beet is thus a potential crop from which fuel alcohol can be accessed after a multi-tower pressure distillation plant. An exotic sugar beet variety SZ-35 was evaluated in the present study for optimization of pre-treatment followed by its ethanolic fermentation.