A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 2005

A heterotrophic marine diatom Nit:sclria alba was studied in shake flask, batch and fed batch fermenter to get increased biomass. Enhanced growth i.e. Increase in biomass was achieved with increasing concentration of glucose. The increasing glucose concentration had positive influence on biomass up to 3% i.e. the percent increase as compared to shake flask experiment was 60.8, 61.9 and 65.5 with 0.6%, 2% and 3% respectively. As the glucose concentration increased, it was found that one-third of the substrate was remaining even at the end of cultivation. Substrate inhibition concentration was found to be at 4% glucose level which was reflected in decrease in biomass as well as specific growth rate as 5.83 g/L and 0.0056 h " respectively. Fed batch fermentation with 5.3% glucose concentration was done such that residual glucose concentration would be lower than inhibitory level of 4% at all times. High density of biomass i.e.10.93 g/L as well as effective substrate utilization was observed. Only 0.01 g/L glucose remained at the end of 50 hrs. The increase in cell biomass productivity is 127 % with the fed batch as compared to that from batch reactor. Simulations were done for the same using Berkeley Madonna Software and the fit for fed batch fermentation gave a R2 value of 0.94.