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Research articles

ScienceAsia 45 (2019): 3-9 |doi: 10.2306/scienceasia1513-1874.2019.45.003

Comparison of yeast extract prepared by autolysis or steam explosion as a cheap nutrient supplement for very high gravity ethanol fermentation of cassava starch

Thanaporn Palasaka, Sarintip Sooksaib, Ancharida Savarajarac,*

ABSTRACT:     Very high gravity fermentation of saccharified cassava starch containing 280 g/l reducing sugar to ethanol by the osmotolerant Saccharomyces cerevisiae G2-3-2 strain required supplementation with inorganic nutrients (KH2PO4, (NH4)2HPO4, and MgSO4 ? 7 H2O and yeast extract (YE) to maximize the ethanol production level and rate. Comparison of the YE prepared by the autolysis of spent brewer?s yeast at either 50 °C for 24 h (A-YE) or steam explosion at 200 °C for 20 min (SE-YE), as a replacement for commercial yeast extract (C-YE) at 7.5 g/l, revealed that A-YE gave a slightly higher ethanol concentration (113.85 g/l) than the SE-YE (107.81 g/l), and was comparable to that obtained with the C-YE (113.14 g/l). At the optimal concentration of A-YE supplementation (5.23 g/l), the ethanol concentration in the ferment reached 115.77 g/l at 24 h, an ethanol productivity of 4.82 g/l/h

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a Biotechnology Program, Faculty of Science, Chulalongkorn University, Bangkok 10330 Thailand
b The Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Bangkok 10330 Thailand
c Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok 10330 Thailand

* Corresponding author, E-mail: sanchari@chula.ac.th

Received 23 Mar 2018, Accepted 27 Feb 2019