Optimization of Agitation and Aeration for Very High Gravity Ethanol Fermentation from Sweet Sorghum Juice by Saccharomyces cerevisiae Using an Orthogonal Array Design

Abstract

Optimization of three parameters: agitation rate (A; 100, 200 and 300 rpm), aeration rate (B; 0.5, 1.5 and 2.5 vvm) and aeration timing (C; 2, 4 and 6 h), for ethanol production from sweet sorghum juice under very high gravity (VHG, 290 g L−1 of total sugar) conditions by Saccharomyces cerevisiae NP 01 was attempted using an L9 (34) orthogonal array design. The fermentation was carried out at 30 °C in a 2-L bioreactor and the initial yeast cell concentration was approximately 2 × 107 cells mL−1. The results showed that the optimum condition for ethanol fermentation should be A2B3C2 corresponding to agitation rate, 200 rpm; aeration rate, 2.5 vvm and aeration timing, 4 h. The verification experiments under the optimum condition clearly indicated that the aeration and agitation strategies improved ethanol production. The ethanol concentration (P), productivity (Qp) and ethanol yield (Yp/s) were 132.82 ± 1.06 g L−1, 2.55 ± 0.00 g L−1h−1 and 0.50 ± 0.00, respectively. Under the same condition without aeration (agitation rate at 200 rpm), P and Qp were only 118.02 ± 1.19 g L−1 and 2.19 ± 0.04 g L−1h−1, respectively while Yp/s was not different from that under the optimum condition.

Optimization of Nitrogen and Metal Ions Supplementation for Very High Gravity Bioethanol Fermentation from Sweet Sorghum Juice Using an Orthogonal Array Design

“…However, the concentrations of the three essential elements (Zn ) in the juice were lower than those recommended for ethanol fermentation in many literatures [8,16,20,23,[28][29][30]32]. Note: a Data from [16].…”

“…According to many literature reviews, the concentrations of Zn [8,16,20,23,[28][29][30]32]. Therefore, the preliminary study on nutrient supplementation was carried out at the lowest and highest nutrient concentrations described above.…”

“…KKU 40) by a sugarcane extractor was obtained from Division of Agronomy, Faculty of Agriculture, Khon Kaen University, Thailand. The juice containing 18 °Bx of total soluble solids was concentrated to 75 °Bx and stored at 4 °C [20,31].…”

“…Nitrogen is necessary for yeast growth and influences the rate of ethanol production and ethanol tolerance [8]. Yeast extract, a complex nutrient, is widely used as a nitrogen source for yeast growth as well as a nutrient supplement for ethanol production [16,19,20] and lactic acid production [21]. Apart from carbon and nitrogen sources, micronutrients or trace elements are also important factors for promoting cell growth and ethanol fermentation, especially under VHG fermentation [22].…”

Utilization of Sweet Sorghum Juice for Efficient 2,3-Butanediol Production by Serratia marcescens H30

“…OAD can efficiently reduce the number of tests and achieve the optimum value. It can also arrange different factors for effective optimization of the experimental conditions (Yang et al 2011;Khongsay et al 2012). The major variables influencing 2,3-BD production were the contents of SSJ, yeast extract, sodium acetate, KH2PO4, MgSO4, MnSO4, and ZnCl2.…”