The applications of thermotolerant microorganisms in the production of lignocellulosic bioethanol is the key factor for successful simultaneous saccharification and fermentation process. Thus, this study aimed to isolate a thermotolerant yeast strain that was able to convert both glucose and xylose into ethanol. An analysis based on D1/D2 region of the large-subunit ribosomal DNA identified the isolated strain namely as Pichia kudriavzevii UniMAP 3-1. The growth of this newly isolated yeast was tested with fermentation temperature at 30°C and 40°C on xylose and glucose. P. kudriavzevii UniMAP 3-1 was able to ferment xylose to ethanol at both 30°C and 40°C with a yield of 0.013 g/g and 0.019 g/g with concomitant xylitol yield of 0.24 g/g and 0.25 g/g, respectively. Fermentation of glucose to ethanol was also tested at 30°C and 40°C and the yields were 0.42 g/g and 0.41 g/g, respectively. The potential of this thermotolerant yeast to be used in high-temperature fermentation in both glucose and xylose are proven in this study.

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Abstract-Acetoacetyl-CoA thiolase (AACT, β-ketothiolase) is an enzyme that catalyzes the biological Claisen condensation of two molecules of acetyl-CoA to form acetoacetyl-CoA. In plants, AACT is known to be involved in the early step of mevalonate pathway which is essential in producing isoprenoid compounds such as sterols, carotenoids and growth regulators. In order to study this gene, we attempt to clone the gene from oil palm. The AACT gene was cloned from a genomic library of oil palm using a homologous probe from the AACT cDNA clone.

The decreasing reserves of non-renewable energy especially fossil fuel has led to an urgent need to establish alternative fuels. Ethanol is one of the energies explored, which can be generated by fermentation method. The use of environmentally friendly material such as lignocellulosic biomass to develop a biofuel is significant. Ethanol production at high temperature was preferred as it will significantly reduce the cooling cost involved. Thus, the use of thermotolerant strain in the fermentation process was recommended. In this study, separate hydrolysis and fermentation (SHF) was employed to produce ethanol from 2% sodium hydroxide-treated rice straw using cellulase enzyme, and fermented by a thermotolerant K. marxianus UniMAP 1-1 strain. The fermentation process was done at two different temperatures, 37°C and 50°C, at pH 4.8. The ethanol yield from both 37°C and 50°C was 0.36 g/g and 0.38 g/g, respectively. K. marxianus UniMAP 1-1 showed a good production of ethanol at elevated temperature. This is the first study reporting ethanol production from rice straw using K. marxianus UniMAP 1-1. Thus, this study can improve our understanding of the development of thermotolerant yeast accountable to the SHF process for ethanol production.