Yeasts from peat in a tropical peat swamp forest in Thailand and their ability to produce ethanol, indole-3-acetic acid and extracellular enzymes

Abstract

This study aimed to isolate and identify yeasts from peat in To Daeng peat swamp forest in southern of Thailand, and to investigate their ability to produce ethanol from glucose and xylose and to produce indole-3-acetic acid (IAA) and extracellular enzymes. A total of 65 yeast strains were obtained from 15 peat samples using an enrichment technique, and 61 strains were identified to be five species belonging to the phylum Ascomycota, namely Cyberlindnera subsufficiens, Debaryomyces fabryi, Meyerozyma guilliermondii, Saturnispora diversa and Schwanniomyces polymorphus var. africanus, and five species of the phylum Basidiomycota, namely Cryptococcus taiwanensis pro tem, Cutaneotrichosporon mucoides, Papiliotrema flavescens, Papiliotrema laurentii and Rhodotorula mucilaginosa. Four strains were unidentified and require further analysis. They differed from the type strain of P. flavescens by two nucleotide substitutions in the D1/D2 region of the LSU rRNA gene and nine nucleotide substitutions in the ITS region. R. mucilaginosa was the most prevalent yeast species, followed by S. polymorphus var. africanus, Cy. subsufficiens and D. fabryi. None of the yeast strains obtained in this study were able to ferment xylose to ethanol, but all ascomycetous yeast strains produced ethanol from glucose in a range of 9.0-58.0 g/L, with Cy. subsufficiens DMKU-YNB42-1 producing the highest ethanol concentration. A total of 62 strains produced IAA in a range of 9.0 to 66.9 mg/L, with the highest IAA produced by R. mucilaginosa DMKU-Y33-A. Investigation of the production of cellulases, xylanase, pectinase, amylase, protease and lipase revealed that all 65 yeast strains produced at least one extracellular enzyme, a lipase.

Yeasts of the soil – obscure but precious

“…Similarly, Asian soils were mainly studied as the source of novel yeast species but the information on the distribution of other species is scarce (e.g. Jaiboon, Lertwattanasakul, Limtong, & Limtong, ; Landell et al, ; Limtong, Yongmanitchai, Kawasaki, & Fujiyama, ; Limtong, Yongmanitchai, Tun, Kawasaki, & Seki, ). Forest soils in the Southern Hemisphere are strongly under‐sampled.…”

Yeast communities of secondary peat swamp forests in Thailand and their antagonistic activities against fungal pathogens cause of plant and postharvest fruit diseases

“…The organic matter content of the soil samples collected from KK PSF varied considerably in the range of 6.45-93.64%. Therefore, based on the organic matter content as suggested by Huat et al [51], only three samples: S03, S04 and S05, whose organic content was greater than 30%, were considered to be peat soils, whereas, the other samples were soils. The soil samples collected from RBG PSF appeared to contain low amounts of organic matter (2.14-10.51%), therefore, these samples were designated as soils.…”

“…Not only from Thailand but also from tropical regions all over the world, there have been few reports on yeast communities of tropical PSFs. Jaiboon et al [51] reported cultivable yeast species isolated by the enrichment technique from peat at different depths from To Daeng PSF. This forest, which is located in the southern Thailand, is the largest and most fertile primary PSF in the country.…”

Teunia siamensis f.a., sp. nov., a novel tremellaceous yeast species isolated from soil in a secondary peat swamp forest area

“…Peat swamp forest (PSF) is a unique ecosystem where peat is formed from the incomplete decomposition of organic matter due to waterlogged conditions [6,7]. This ecosystem is important as it provides global carbon storage for soil organic matter; however, little is known about its microbial diversity [7].…”

“…Based on their plant communities, tropical PSFs are classified as primary or secondary, with primary PSFs consisting of fertile areas with a high diversity of plant species. Secondary PSFs are primary PSFs that have been compromised by drought, wildfires and human activities, such as logging, land conversion and water drainage for agriculture, resulting in a decrease in the richness of plant species [7,10] studies on yeast diversity in primary and secondary PSFs in Thailand have been carried out recently [6,10], with five novel yeast species, Nakazawaea todaengensis, Saturnispora kantuleensis, Candida kantuleensis, Candida xylosifermentans and Cryptotrichosporon siamense, proposed as a result [11][12][13][14][15].…”