抄録
Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants known, because of their multifunctionality and biocompatibility. In order to attain an efficient production of MELs, Pseudozyma parantarctica JCM 11752T, which is a newly identified strain of the genus, was examined for the productivity of MELs at different culture conditions. The yeast strain showed significant cell growth and production of di-acylated MELs even at 36°C. In contrast, on conventional high-level MEL producers including P. rugulosa, the MEL yield considerably decreased with an increase of the cultivation temperature at over 30°C. On P. parantarctica, soybean oil and sodium nitrate were the best carbon and nitrogen sources, respectively. Under the optimal conditions on a shake-flask culture at 34°C, the amount of di-acylated MELs reached over 100 g/L by intermittent feeding of only soybean oil.
Interestingly, the yeast strain produced tri-acylated MELs as well as di-acylated ones when grown on the medium containing higher soybean oil concentrations than 8% (vol/vol). The production of tri-acylated MELs was significantly accelerated at between 34 and 36°C. With 20 % (vol/vol) of soybean oil at 34°C, the yield of tri-acylated MELs reached 22.7 g/L. The extracellular lipase activity considerably depended on the culture temperature, and became the maximum at 34°C; this would bring the accelerated production of tri-acylated MELs. Accordingly, the present strain of P. parantarctica provided high efficiency in MEL production at elevated temperatures compared to conventional MEL producers, and would thus be highly advantageous for the commercial production of the promising biosurfactants.
