Sporeformers are sources of a large number of industrially important biological products including enzymes, antibiotics, and bioinsecticides. Cultivation of these microorganisms to high cell densities offers potential for enhancing the rates of formation as well as the concentration of the desired products in the fermentation broths in bioreactors. With this objective, investigations have been carried out involving fed-batch cultivation of Bacillus thuringiensis, which is known to produce an insecticidal crystal protein during sporulation. With appropriate management of aeration and nutrient supply, it was possible to grow the cells to > 50 g DW/l density. Nevertheless, the achievement of high cell density did not enhance the formation of crystal protein in the same proportion as the cell concentration. Further examination of this system suggested a complex interplay of energetic requirements for protein turnover during sporulation. Energy reserve material, poly-beta-hydroxybutyric acid, appeared to be linked to formation of spores and crystal protein during the sporulation phase.

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A microbial isolate showed strong antibacterial and antifungal activity against various multidrug-resistant test organisms. Based on physiological and biochemical characteristics and 16S ribosomal RNA sequence homology studies, it was found to be similar to Streptomyces capoamus (gene sequence similarity 98%). The antifungal metabolite was produced majorly intracellularly. The active metabolite was extracted and purified by gel filtration chromatography and highperformance liquid chromatography (HPLC). Partial chemical characterization of the active compound has been completed. To the best of our knowledge this strain has not been reported to produce antifungal compounds. The paper presented here describes the activity profile of the strain, classical medium optimization, and purification of the antifungal compound.

An actinomycin-D producing strain was isolated from soil and characterized as Streptomyces sindenensis. The culture was subjected to UV irradiation and a mutant with 400% higher actinomycin-D production was isolated (400 mg/l -1 as compared to 80 mg/l -1 produced by the parent). Production medium was optimized and antibiotic yield with the mutant was enhanced to 850 mg/l -1 which is 963% higher as compared with the parent.

Two biologically active microbial strains were isolated from soil samples collected from different geographical areas of India. These strains were characterized as Streptomyces halstedii MTCC 6817 and Streptomyces anulatus MTCC 6818. Active compounds were extracted from the purified fermented broth and one of them was chemically characterized as actinomycin-D. Though these two strains produced the same antibiotic, their nutritional requirements vary substantially. For S. halstedii, a medium containing 1.5% fructose, 0.05% Nacetylglucosamine, and basal production medium, gave the maximum titre, 754% higher, as compared to production medium alone. In the case of Streptomyces anulatus, maximum antibiotic production was attained with a production medium containing 1.5% galactose and 0.05% L-asparagine monohydrate.