METHODS: Different combinations of nitrogen sources, salts and pre-culture combinations were applied in the fermentation media and lovastatin yield was analysed chromatographically.
RESULT: The exclusion of MnSO4 ·5H2O, CuSO4·5H2O and FeCl3·6H2O were shown to significantly improve lovastatin production (282%), while KH2PO4, MgSO4·7H2O, and NaCl and ZnSO4·7H2O were indispensable for good lovastatin production. Simple nitrogen source (ammonia) was unfavourable for morphology, growth and lovastatin production. In contrast, yeast extract (complex nitrogen source) produced the highest lovastatin yield (25.52 mg/L), while powdered soybean favoured the production of co-metabolites ((+)-geodin and sulochrin). Intermediate lactose: yeast extract (5:4) ratio produced the optimal lovastatin yield (12.33 mg/L) during pre-culture, while high (5:2) or low (5:6) lactose to yeast extract ratio produced significantly lower lovastatin yield (7.98 mg/L and 9.12 mg/L, respectively). High spore concentration, up to 107 spores/L was shown to be beneficial for lovastatin, but not for co-metabolite production, while higher spore age was shown to be beneficial for all of its metabolites.
CONCLUSION: The findings from these investigations could be used for future cultivation of A. terreus in the production of desired metabolites.
RESULTS: A thermostable organic solvent-tolerant protease producer had been identified as Bacillus subtilis strain Rand, based on the 16S rRNA analysis conducted, as well as the morphological characteristics and biochemical properties. The production of the thermostable organic solvent-tolerant protease was optimized by varying various physical culture conditions. Inoculation with 5.0% (v/v) of (AB600 = 0.5) inoculum size, in a culture medium (pH 7.0) and incubated for 24 h at 37 degrees C with 200 rpm shaking, was the best culture condition which resulted in the maximum growth and production of protease (444.7 U/ml; 4042.4 U/mg). The Rand protease was not only stable in the presence of organic solvents, but it also exhibited a higher activity than in the absence of organic solvent, except for pyridine which inhibited the protease activity. The enzyme retained 100, 99 and 80% of its initial activity, after the heat treatment for 30 min at 50, 55, and 60 degrees C, respectively.
CONCLUSION: Strain Rand has been found to be able to secrete extra-cellular thermostable organic solvent-tolerant protease into the culture medium. The protease exhibited a remarkable stability towards temperature and organic solvent. This unique property makes it attractive and useful to be used in industrial applications.
SIGNIFICANCE AND IMPACT OF THE STUDY: The bacteria isolated from unusual dwellings such as the cockroaches' gut are a useful source of antibacterial and antiamoebal molecules. These are remarkable findings that will open several avenues in our search for novel antimicrobials from unique sources. Furthermore studies will lead to the identification of molecules to develop future antibacterials from insects.