Production of lipoic acid (LA) is undergoing a paradigm shift with significant preference for fer... more Production of lipoic acid (LA) is undergoing a paradigm shift with significant preference for fermentative production over conventional chemical synthesis. However, low product yield triggers the importance of the development of an efficient cell disruption method as a critical step in its recovery. In this paper, we report screening of various physical, mechanical and chemical methods of cell disruption for high release of LA from S. cerevisiae. Among these methods, ultra sonication and EDTA were found to be most effective. The optimized ultra sonication process with respect to cell density (10g/L), time of sonication (3 min), acoustic power (50 W) and duty cycle (70%) resulted in maximum release of 11.4 mg/g DCW of LA in one cycle. Although batch release of LA gave a maximum yield of 42.5 mg/g DCW in six cycles of ultra sonication, the high energy consumption during ultra sonication (5400 kJ/ m) was discouraging during scale-up. Hence, incubation 3 of the cell mass with 50 mM EDTA for 2 h which released 25.59 mg/g DCW of LA was preferred as the method of choice for subsequent work. Assuming LA release during ultra sonication and EDTA permeabilization to follow first order kinetics, the rate constants obtained were 0.011 /min and 0.074 min respectively.
Scale up studies for production of lipoic acid (LA) from Saccharomyces cerevisiae have been repor... more Scale up studies for production of lipoic acid (LA) from Saccharomyces cerevisiae have been reported in this paper for the first time. LA production in batch mode was carried out in a stirred tank bioreactor at varying agitation and aeration with maximum LA production of 512 mg/L obtained at 350 rpm and 25 % dissolved oxygen in batch culture conditions. Thus, LA production increased from 352 mg/L in shake flask to 512 mg/L in batch mode in a 5 L stirred tank bioreactor. Biomass production under these conditions was mathematically explained using logistic equation and data obtained for LA production and substrate utilization were successfully fitted using Luedeking-Piret and Mercier's models. The kinetic studies showed LA production to be growth associated. Further enhancement of LA production was carried out using fed-batch (variable volume) and semi-continuous modes of fermentation. Semi-continuous fermentation with three feeding cycles of sucrose effectively increased the production of LA from 512 to 725 mg/L.
Production of lipoic acid (LA) is undergoing a paradigm shift with significant preference for fer... more Production of lipoic acid (LA) is undergoing a paradigm shift with significant preference for fermentative production over conventional chemical synthesis. However, low product yield triggers the importance of the development of an efficient cell disruption method as a critical step in its recovery. In this paper, we report screening of various physical, mechanical and chemical methods of cell disruption for high release of LA from S. cerevisiae. Among these methods, ultra sonication and EDTA were found to be most effective. The optimized ultra sonication process with respect to cell density (10g/L), time of sonication (3 min), acoustic power (50 W) and duty cycle (70%) resulted in maximum release of 11.4 mg/g DCW of LA in one cycle. Although batch release of LA gave a maximum yield of 42.5 mg/g DCW in six cycles of ultra sonication, the high energy consumption during ultra sonication (5400 kJ/ m) was discouraging during scale-up. Hence, incubation 3 of the cell mass with 50 mM EDTA for 2 h which released 25.59 mg/g DCW of LA was preferred as the method of choice for subsequent work. Assuming LA release during ultra sonication and EDTA permeabilization to follow first order kinetics, the rate constants obtained were 0.011 /min and 0.074 min respectively.
Scale up studies for production of lipoic acid (LA) from Saccharomyces cerevisiae have been repor... more Scale up studies for production of lipoic acid (LA) from Saccharomyces cerevisiae have been reported in this paper for the first time. LA production in batch mode was carried out in a stirred tank bioreactor at varying agitation and aeration with maximum LA production of 512 mg/L obtained at 350 rpm and 25 % dissolved oxygen in batch culture conditions. Thus, LA production increased from 352 mg/L in shake flask to 512 mg/L in batch mode in a 5 L stirred tank bioreactor. Biomass production under these conditions was mathematically explained using logistic equation and data obtained for LA production and substrate utilization were successfully fitted using Luedeking-Piret and Mercier's models. The kinetic studies showed LA production to be growth associated. Further enhancement of LA production was carried out using fed-batch (variable volume) and semi-continuous modes of fermentation. Semi-continuous fermentation with three feeding cycles of sucrose effectively increased the production of LA from 512 to 725 mg/L.
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Papers by Shilpa Jayakar