Potential of Thermotolerant Ethanologenic Yeasts Isolated from ASEAN Countries and Their Application in High- Temperature Fermentation

Abstract

Thermotolerant ethanologenic yeasts receive attention as alternative bio-ethanol producers to traditionally used yeast, Saccharomyces cerevisiae. Their utilization is expected to provide several benefits for bio-ethanol production due to their characteristics and robustness. They have been isolated from a wide variety of environments in a number of ASEAN countries: Thailand, Vietnam, Laos, and Indonesia. One of these yeasts, Kluyveromyces marxianus has been investigated regarding characteristics. Some strains efficiently utilize xylose, which is a main component of the 2nd generation biomass. In addition, the genetic basis of K. marxianus has been revealed by genomic sequencing and is exploited for further improvement of the strains by thermal adaptation or gene engineering techniques. Moreover, the glucose repression of K. marxianus and its mechanisms has been investigated. Results suggest that K. marxianus is an alternative to S. cerevisiae in next-generation bio-ethanol production industry. Indeed, we have succeeded to apply K. marxianus for bio-ethanol production in a newly developed process, which combines high-temperature fermentation with simultaneous fermentation and distillation under low pressure. This chapter aims to provide valuable information on thermotolerant ethanologenic yeasts and their application, which may direct the economic bioproduction of ethanol and other useful materials in the future.Recently, thermotolerant microorganisms were found among mesophiles with optimum growth temperatures that are 5-10°C higher than those of the typical mesophilic strains Fuel Ethanol Production from Sugarcane 122 Potential of Thermotolerant Ethanologenic Yeasts Isolated from ASEAN Countries… http://dx.doi.org/10.5772/intechopen.79144 123Recently, there have been several reports on ethanol production at high temperatures using P. kudriavzevii (formerly known as I. orientalis). Several P. kudriavzevii strains were reported to grow and produce high levels of ethanol at high temperatures. The strain DMKU 3-ET15 was isolated from traditional fermented pork sausage in Thailand by an enrichment technique in a medium supplemented with 4% ethanol at 40°C. The strain produced 78.6 g/L ethanol from 180 g/L glucose at 40°C [20]. The strain KVMP10 that was isolated from soil located beneath apple trees for ethanol production from orange peel achieved 54 g/L ethanol at 42°C [48]. Strain RZ8-1 that was recently isolated from various samples collected from plant orchards in Thailand produced 33.8 g/L ethanol from 160 g/L glucose at 40°C [49].

Enhancement of Thermal Resistance by Metal Ions in Thermotolerant Zymomonas mobilis TISTR 548

“…However, industrial scale bioethanol production requires a more costeffective process to be economically competitive. High-temperature fermentation (HTF; which enables fermentation at a temperature 5-10 • C higher than that used in the conventional process) may reduce (1) cooling cost, (2) running cost at the simultaneous saccharification and fermentation stage, and (3) contamination risks (Abdel-Banat et al, 2010;Kosaka et al, 2018). Bioethanol production by HTF requires high-efficiency ethanol production and thermotolerant microorganisms.…”

MIG1 as a positive regulator for the histidine biosynthesis pathway and as a global regulator in thermotolerant yeast Kluyveromyces marxianus

“…There have been several studies on sugar utilization and ethanol production by K . marxianus at high temperatures 1,2,4,5 that were carried out with the aim of establishing high-temperature fermentation, which has advantages including reduction of cooling costs, prevention of contamination and reduction of enzymatic hydrolysis cost 5–7 . The regulation of some genes related to glucose repression in K .…”

Process Intensification in Bio-Ethanol Production–Recent Developments in Membrane Separation

“…However, in order to be profitable in a small ethanol production facility, it is essential to develop an innovative technology for each step of the ethanol production process. Here, we introduce a high-temperature fermentation (HTF) technology that has several benefits, such as reduced cooling costs, reduced microbial contamination, and reduced amounts of hydrolytic enzymes used in simultaneous saccharification and fermentation (SSF) [24,25]. Fermentation is an exothermic reaction that requires cooling of the reactor, as the temperature inside the reactor rises to around 313 K. Otherwise, such high temperatures cause prevention of the fermentation ability of ethanol-producing microorganisms or cell death.…”

“…On the other hand, thermotolerant microorganisms capable of efficiently fermenting and producing ethanol at high temperatures are indispensable for HTF technology. We have isolated and characterized many thermotolerant yeasts from joint research from southeast Asian countries, centering on Thailand [25]. Among them, Kluyveromyces marxianus DMKU3-1042, isolated in Thailand, can grow at 321 K and showed high ethanol productivity up to about 316 K when glucose was used as a carbon source.…”