Carbon mass balance analysis of biosurfactant, scophorose lipid, fermentation by Torulopsis bombicola

Abstract

Biosurfactant fermentation was investigated using Torulopsis bombicola (ATCC 22214). Torulopsis bombicola produced the biosurfactant, sophorose lipid, to 80 g/l (Yp/s=0.33) in batch culture containing 11\% glucose and 10\% soybean-oil as carbon and energy sources. There was no considerable amount of by-products and alcohol, organic acid in the culture broth. From the result of carbon mass balace analysis using mass spectrometer for monitoring $CO_2$ evolved as a gas during culture, almost all, over 90\%, of input carbon could have been accounted for, channeling to cell, product, and $CO_2$ gas. Carbon fraction channeled to cells and product was about 13\% and 37\%, respectively in batch culture containing 11\% glucose and 10\% soybean oil as carbon and energy sources and 10\% soybean oil as a sole carbon source. However, in batch culture of 10\% glucose as a sole carbon source, only 9\% of input carbon was incorporated into the product and 27\% of input carbon was incorporated into the cells. Oil intermittent feeding fedbatch culture was carried out to reduce the carbon fraction of $CO_2$ gas and increase the product conversion yield. From the result of oil intermittent feeding fed-batch culture, the carbon fracion of product was increased to 60\% compared to 37\% of batch culture, and that of $CO_2$ gas was decreased to about 30\% from 50\% of batch culture. From the oil continuous feeding fed-batch culture for understanding oil concentration effect on sophorose lipid productin, the oil flow rate, i.e., oil concentration in the culture broth, influenced the product conversion yield and production rate. The greatest product corsion yield, 61\%, was obtained at the slowest flow rate, 1.0ml/hr. The faster the flow rate the lower the product conversion yield. The volumetric and specific production rate was the highest at 2.1 ml/hr, and the faster flow rate than this decreased the production rate. The effect of specific growth rate and oil concentration on sophoros...