ที่มา:วิทยาสารเกษตรศาสตร์ สาขา วิทยาศาสตร์

หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Physiological Study and Alcohol Oxidase Gene(s) of Thermotolerant Methylotrophic Yeasts Isolated in Thailand)

ผู้เขียน:ดร.นันทนา สีสุข, รองศาสตราจารย์, ดร.สาวิตรี ลิ่มทอง, ศาสตราจารย์, Hiroya Yurimoto, Yasuyoshi Sakai, Nobuo Kato

สื่อสิ่งพิมพ์:pdf

Abstract

Two thermotolerant methylotrophic yeasts, Candida sithepensis sp. nov. and Pichia siamensis sp. nov. isolated in Thailand were studied for their physiology and alcohol oxidase gene(s). Optimum and maximum temperatures for growth on methanol of C. sithepensis sp. nov. were 34?C and 37?C whereas those of P. siamensis sp. nov. were 37?C and 40?C, respectively. Effect of methanol on the methylotrophic growth of the two yeast strains was investigated within the ranges of 0.25% to 2% (v/v) methanol. At 34?C, C. sithepensis sp. nov. exhibited a decline in ?max from 0.16 h-1 to 0.13 h-1 with respect to increase in methanol concentration. When cultivated at 37?C, the ?max of C. sithepensis sp. nov. was found to be drastically decreased from 0.16 h-1 to 0.10 h-1 within the same ranges of methanol concentration studied. P. siamensis sp. nov. showed an insignificant decrease of ?max with respect to an increase in methanol supplement when cultivated at 37?C. Key enzymes involved in methanol dissimilatory pathway, i.e., alcohol oxidase (AOD), glutathione-dependent formaldehyde dehydrogenase (FLD), formate dehydrogenase (FDH) and catalase (CAT) of the two yeasts were assessed. As for the favorable growth of C. sithepensis sp. nov. at its optimum temperature, fairly high level of specific AOD activity was observed but lower level of specific AOD activity was exhibited at maximum temperature. In contrast, specific FLD and FDH activity profiles were found to be higher when the yeast C. sithepensis sp. nov. was grown at its maximum temperature compared to the methylotrophic growth at its optimum temperature. Catalase production appeared to be slightly disturbed under all conditions studied. In case of P. siamensis sp. nov., stationary phase growth under low methanol supplement at its optimum temperature appeared soon after 24h cultivation. Nucleotide sequences of AOD gene(s) of the two yeasts were investigated. C. sithepensis sp. nov. showed two AOD genes designated as AOD1 and AOD2 whereas P. siamensis sp. nov. revealed only one AOD gene within the genome.

Article Info

Agriculture and Natural Resources -- formerly Kasetsart Journal (Natural Science), Volume 040, Issue 1, Jan 06 - Mar 06, Page 121 - 135 |  PDF |  Page