Medium Optimization for beta-Galactosidase Production by a Thermotolerant Yeast

作者：Am aiam Sirinda; Khanongnuch Chartchai^*

来源：Chiang Mai Journal of Science, 2015, 42(4): 840-849.

• beta-galactosidase
• thermotolerant yeast
• medium optimization
• 2-level factorial experimental design
• central composite design

Kluyveromyces sp. CK8 was previously isolated from rotten fruit in northern Thailand and found to be capable of growing at 45 degrees C. This research aimed to identify the yeast isolate and to optimize its production of beta-galactosidase in synthetic medium using lactose as the sole carbon source. Molecular identification via phylogenetic analysis, based on comparative sequence analysis of the 26S rRNA gene at the D1/D2 domain, revealed that isolate CK8 was Kluyveromyces marxianus. The yeast isolate produced beta-galactosidase 5.33 U/ml culture when cultivated at 37 degrees C for 18 h in Yeast-Malt extract (YM) medium containing 1% (w/v) lactose as the sole carbon source. Optimization of medium composition for enzyme production was conducted using 2-Level Factorial experimental design to determine the most relevant variables of the culture medium composition. Among five parameters, yeast extract, (NH4)(2)SO4 and KH2PO4 were significant effectors at p<0.05. A central composite design (CCD) and response surface plot predicted the highest beta-galactosidase activity of 8.94 U/ml culture in the medium containing (g/l) of the following: yeast extract (0.23), (NH4)(2)SO4 (9.64), KH2PO4 (7.0), lactose (20) and MgSO4 center dot 7H(2)O (0.1). A validation time course culture study conducted for 18 h in the optimal medium found that the actual maximum value of enzyme activity was 8.82 U/ml culture which is 98.66% of the predicted value.

• 出版日期2015-10