การผลิตแคโรทีนอยด์จากยีสต์โดยใช้กลีเซอรอลเหลือทิ้งที่ได้จากการผลิตไบโอดีเซลเป็นแหล่งคาร์บอน

บทคัดย่อ

The usage of waste glycerol obtained from biodiesel production is a big challenge as this glycerol is not suitable for foods and cosmetics applications. Therefore, fourteen strains of red yeasts from the culture collection of Thailand Institute Scientific and Technological Research (TISTR) were screened for carotenoids production in yeast malt-extract medium (YM), basal medium supplemented with either pure glycerol (BMP) or waste glycerol (BMW) as the sole carbon source in a 250-mL shake-flask containing 50 mL medium under the cultivation conditions; incubation at 25oC, shaking speed of 250 rpm for 5 days. The results showed that only eleven strains could grow and produce carotenoid in YM while nine strains were observed in BWG and BMW. Among 9 strains, we found that Sporobolomyces pararoseus TISTR5213 produced the maximum of total carotenoids at 5.21?0.39, 1.72?0.16 and 1.77?0.02 mg/L, in YM, BMP and BMW, respectively. Variable medium components of BMW were selected in accordance with the Plackett-Burman experimental design with only one factor of waste glycerol being significant (p<0.05) on the carotenoid production by Sporobolomyces pararoseus TISTR5213. The optimization conditions for physical factors (pH and temperature levels) were then combined in further studies through the response surface methodology (RSM) approach via a central composite design (CCD). The results revealed that three factors affected on carotenoid production with the (R2) of 0.9911 or 99.11%. The optimal conditions for carotenoids production were; waste glycerol 55.04 g/L, initail pH 5.63 and 24.01oC. Under optimal conditions, the carotenoids content of Sporobolomyces pararoseus TISTR5213 reached to 53.70 g/L which increased from the predicted value (46.29 mg/L) of 16.01% or higher than non-optimized conditions about 2,933%. The scale-up of carotenoids production in the 3.0-L air-lift fermenter with a working volume of 2.0 L, was also studied using the optimal conditions which obtained from the shake-flask scale at aeration rate of 2.0 vvvm. The results showed that under uncontrolled pH condition the carotenoids content of 46.67?0.31 mg/L and dried cell weight (DCW) of 6.73?0.06 g/L were obatined after 5 days of cultivation time. While, the controlled pH condition at 5.63, the carotenoid content and DCW were slightly increased and reached to the maximum after 7 days of cultivation time. The carotenoids content of 46.08?0.11 mg/L and DCW of 14.11?0.07 g/L were obtained. These results indicated that waste glycerol from biodiesel production process shows high potential as a sole of carbon for carotenoids production by Sporobolomyces pararoseus TISTR5213.

คำสำคัญ