Use of response surface design in the optimization of starter cultures for enhanced rhamnolipid production by Pseudomonas nitroreducens

The development and management of an inoculum through various stages has a definite effect on subsequent performance and economics of a microbial process. To achieve this, application of response surface modeling in the optimization of the primary and secondary inoculum build-up of Pseudomonas nitroreducens for enhanced rhamnolipid production was presented in this study. This involved systematic studies to understand the individual, cumulative and mutual interactive effects of the two parameters, inoculum age and size on rhamnolipid production. The optimal combination of factors was as follows: primary inoculum age = 61 h, primary inoculum size = 1% (v/v), secondary inoculum age = 28 h and secondary inoculum size = 20% (v/v). The model predicted a maximum rhamnolipid yield of 7.944 g/L. This was as a result of strong interaction between secondary inoculum age and size. The subsequent experiments with the optimized conditions yielded 6.97 g/L of rhamnolipid, which is very consistent with the prediction made by the model used.Keywords: Biosurfactants, inoculum age, inoculum size, Pseudomonas nitroreducens, response surface design, rhamnolipidAfrican Journal of Biotechnology Vol. 12(19), pp. 2611-261

Culture conditions for the production of a tannase of Aspergillus tamarii IMI388810 (B)

Aspergillus tamarii IMI388810 (B) a tannic acid degrading fungus was isolated from soil inundated by effluent of a tannery at Oji River local Government Area of Enugu State, Nigeria. It was identified byCABI Bioscience, United Kingdom as A. tamarii with accession number of IMI 388810 (B). This fungus produced tannase in a fermentation medium M containing tannic acid as the only carbon source. Time course of enzyme synthesis by the fungus showed that the enzyme production followed logarithmic growth phase with maximum enzyme yield being obtained after 6 days corresponding to the culture pH of 3.8