The effects of total carbohydrate, total protein, carbohydrate/protein ratio, amino acid contents, initial pH and aeration on biomass yield product of Bacillus thuringiensis subsp. kurstaki was investigated. The bacteria were cultured in economical media comprising agricultural products and by-products including fishmeal, cottonseed meal, defatted soybean meal, cornsteep liquor, yeast extract, scotafeme, sorghum and peptone as protein sources and glucose and beet molasses as carbohydrate sources. The results indicated the presence of a direct correlation between yield biomass and carbohydrate/protein (C/N) ratio as well as the glutamic acid content of the media. The highest biomass was produced in the media providing 0.4 – 0.5 C/N ratio and 13.9% glutamic acid. A pH range of 7.0 to 8.0 was needed for high yield production. The optimal ratio for culture volume to flask size and shaking speed were 1/5 and 250 rpm, respectively. The biochemical factors described can be considered as the minimal criteria to evaluate culture media for biomass production from Bacillus thuringiensis subsp. kurstaki.