Dhanya Gangadharan

Genome shuffling of Lactobacillus delbrueckii mutant and Bacillus amyloliquefaciens through protoplasmic fusion for L-lactic acid production from starchy wastes.

Current study was focused on the development of a non-fastidious lactic acid producing strain having better growth rate, low pH tolerance and good productivity by genome shuffling of a mutant strain of Lactobacillus delbrueckii NCIM 2025 and an amylase producing non-fastidious Bacillus amyloliquefaciens ATCC 23842. After the third cycle of the protoplast fusion, lactic acid production by few fusants was monitored and the best fusant was selected for further studies. Optimization of the important process parameters for lactic acid production was conducted using Plackett-Burman design and response surface methodology. Selected fusant could utilize the liquefied cassava bagasse starch directly with minimum nutrient supplementation for lactic acid production. During validation, 40g/L of lactic acid was obtained ( approximately 96% conversion of starch to lactic acid) by using fusant inoculum (3%, v/v) from 83g/L cassava bagasse (starch content 50% w/w) supplemented with yeast extract and peptone (0.2% each, w/v) and the buffering agent (2% CaCO3, w/v).

Edible Oil Cakes

The very sustainability of the growing bioprocess industry depends on the progressive reduction of expensive nutrient inputs into fermentation media. The use of cheap agricultural and food-processing by-products such as oil cakes, as feedstock is highly favored so as to improve the commercial feasibility of bioprocess technology. Due to stringent nutritional requirements of these edible oil cakes as animal feed, there is considerable interest in using them as substrates in the fermentation industry. This chapter will provide an impetus to further research in this area enabling better utilization of edible oil cakes as sources of protein and carbohydrates for economic viability of the bioprocess industry.

Molecular cloning, overexpression and characterization of the raw-starch-digesting α-amylase of Bacillus amyloliquefaciens

Raw starch is the most abundant source of glucose in the world. Therefore, finding enzymes capable of digesting raw starch would find high industrial demand. The α-amylase gene of Bacillus amyloliquefaciens ATCC 23842 was amplified, cloned and overexpressed in Escherichia coli BL21 (DE3) cells. The recombinant enzyme was purified to apparent homogeneity using ion exchange and gel filtration chromatography. The raw-starch digestibility of the purified enzyme was characterized by studying the hydrolysis and adsorption rate on a variety of raw starches (potato, cassava, corn, wheat and rice). The raw-starch digestion was further confirmed by scanning electron microscopy studies, which revealed an effective rate of hydrolysis. The kinetic studies revealed a relatively low Km of 2.76 mg/mL, exhibiting high affinity towards the soluble starch as the most preferred substrate and the inhibition kinetic studies revealed a high Ki value (350 mM).