ABSTRACT
Aims: To evaluate the effect of volumetric oxygen transfer coefficient on the production of xylitol by Debaryomyces nepalensis and to enhance the yield and productivity of xylitol by fed-batch fermentation using xylose as substrate. Place and Duration of Study: All experiments were performed at the Applied and Industrial Microbiology Laboratory, Indian Institute of Technology Madras, from March 2013 to May 2014. Methodology: Batch cultivations were carried out in a 7.5 L fermentor under various oxygen transfer coefficients in the range 12 to 39.6 h-1 in order to understand the effect of oxygen on xylitol production. Fed-batch studies were performed in 2.5 L bioreactor with a working volume of 1 L. The cultures were initially grown as batch cultures. Feed containing xylose and nitrogen source was added to the medium intermittently. Samples were periodically collected at regular intervals of time and the concentrations of xylose, xylitol and glycerol were determined by HPLC. Results: Maximal xylitol yield (0.64 g/g) and productivity (0.43 g/L·h) were obtained at kLa 13.68 h-1. The effect of pH was also studied at this kLa. A pH value of 6.0 was found to be favorable for xylitol accumulation. Fed-batch fermentation involving feeding of xylose and nitrogen source was used for xylitol production by D. nepalensis. Within the fed-batch phase, the yield of xylitol was 0.83 g/g and the productivity was increased to 0.83 g/L.h with a final product concentration of 90 g/L. Conclusion: Higher kLa favors biomass production whereas product formation was favored at lower kLa. Fed-batch process resulted in enhancement of final product concentration by 73%.
ABSTRACT
Studies on the effectiveness of age of in vitro grown seedlings on regenerative response of explants derived from them were conducted in tomato (Solanum lycopersicum L.) cv. PKM-1. The results revealed that cotyledons and hypocotyls of 10 days old seedlings were found to be superior compared to explants collected from 8, 12, 14 days old seedlings when MS medium is supplemented with BAP 1.5 mg/L + Kinetin 1.0 mg/L. These findings could be well exploited for further development of quick regenerative and transformation protocols for the tomato cv.PKM-1.
ABSTRACT
Studies on the effectiveness of various sterilants and culture conditions on in-vitro seed germination in tomato (Solanum lycopersicum L.) cv. PKM-1 revealed that among three sterilants used, surface sterilization of seeds with 5 % NaOCl for 20 minutes was found to be more effective resulting in high germination rate and contamination free cultures. Similarly among the different media and culture conditions considered in the present experiment, MS medium without sucrose with dark incubation for three days recorded lower no. of days (3.3 days) for initiation of germination with 96 % germination. These findings could be well exploited for further development of quick regenerative and transformation protocols for the tomato cv.PKM-1.