Short communication Rapid and enhanced production of ethanol in very high gravity (VHG) sugar fermentation by Saccharomyces cerevisiae: Role of finger millet (Eleusine coracana L.) flour L.V.A. Reddy, O.V.S. Reddy * Department of Biochemistry, S.V. University, Tirupati 517502, India Received 13 July 2005; received in revised form 15 August 2005; accepted 16 August 2005 Abstract The effect of the supplementation of finger millet (Eleusine coracana L.) flour (4–6%, w/v) in the production of ethanol by yeasts in high gravity sugar (30–40%, w/v) containing yeast extract-peptone-malt extract medium was investigated. It was found that the finger millet flour not only reduced the fermentation time (from 5 to 3 days) but also enhanced the ethanol concentration from 10 to 15% (v/v) by better utilization of sugar. The physical and chemical factors of finger millet that may aid in reducing the osmotic stress of high gravity fermentation and as well as enhancing ethanol yield. Production of high ethanol concentration by using VHG sugar fermentation technology eliminates the expensive steps in the conventional process and saves time. # 2005 Elsevier Ltd. All rights reserved. Keywords: High gravity fermentation; Osmotic stress; Finger millet flour; Nutrient supplementation; Ethanol production 1. Introduction The energy crisis necessitates studying and discovering new processes involved in the production of utilizable compounds as alternative energy sources. Among these fermentation to ethanol represents a significant strategy; especially since ethanol has shown promise to partially substitute for gasoline as a fuel [1]. This situation has led many countries including India to field to a policy of blending ethanol at the rate of 5–10% with petrol. This has received world-wide interest to improve and optimize of this process for a quicker and cheaper ethanol production. In India, the main raw material for ethanol production is molasses, which is limited in quantity and requires dilution before it is fermented. And it produces a lot of effluent (12 l per every litre of absolute alcohol) which is very difficult and cost intensive to dispose due to high biological oxygen demand (60,000–80,000 ppm). Hence, one of the alternative methods to reduce effluent is very high gravity (VHG) fermentation technology. It has several advantages like high concentration of ethanol production, increase in plant efficiency and decrease in total energy input, less labour cost and reduced amount of effluent [2]. However, in VHG technology the high sugar concentration affects the yeast metabolism that leads to decrease in final ethanol production. With the customary interest in high gravity fermentation both from quality and economic considerations, research and development efforts are being made to understand the process of alcohol production, excretion and tolerance by fermenting yeast strain. Earlier several researchers studied the increased production of the ethanol by adding certain growth factors and nutrient rich substances, such as soy flour and tamarind waste [3–5]. Similar studies were made in case of wine with additives, such as inositol, catechin and SO 2 [6]. The high concentration of ethanol that is produced in VHG fermentation process ceases yeast growth and is influenced by several factors, which has been comprehensively reviewed [7]. Several investigators have observed that yeast extract [8], ammonium, calcium and magnesium [9] have protective effect either on growth and fermentation or on viability, which stimulate the fermentation rate and ethanol production. High ethanol concentrations (16.2%, v/v) are obtained by using sake yeast in 20 days fermentation [10]. Increased ethanol production with supplementation of horse gram flour in VHG fermentation has been reported from our laboratory [11]. In this connection we tried to investigate the effect of finger millet flour on VHG fermentation. www.elsevier.com/locate/procbio Process Biochemistry 41 (2006) 726–729 * Corresponding author. Tel.: +91 877 2249666x295. E-mail address: ovsreddy@yahoo.com (O.V.S. Reddy). 1359-5113/$ – see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2005.08.011