Growth optimizatio n and metabolite yield of non pathogenic Escherichia coli isolated from the gut of African catfish: Clarias gariepinus

Abstract

Purpose: To investigate the optimum growth and metabolite yield of non-pathogenic Escherichia coli in the gut of African catfish for use as a substitute. Methods: Optimization was statistically carried out for the growth and metabolite yield of non-pathogenic Escherichia coli. Response Surface Design was used to generate three levels of each of the following operational factors viz glucose, peptone water, potassium nitrate (KNO3), Bambara nut, pH and temperature for the production of peptone water–glucose, KNO3–glucose and Bambara nut culture media, respectively. The absorbance was read consecutively for 7 days using a UV-VIS double beam spectrophotometer while the metabolites were identified and analyzed using gas chromatography-MS. Results: Optimum growth and metabolite yield of the non-pathogenic Escherichia coli occurred on the 4th and 7th day in Peptone water–glucose, KNO3–glucose and Bambara nut media, with sequential p-values ranging from 0.115 (quadratic) – 0.002 (linear), 0.370 (linear) – 0.020 (quadratic), 0.470 (linear) – 0.040 (quadratic), respectively. The combination of peptone water (0.9 g), glucose (4.0 g) and pH (7.25) at 37 °C gave the optimum culture conditions for metabolite yield, with 19 classes of metabolites identified. Conclusion: The quadratic model is the suitable predictive model and Peptone water–glucose has optimum metabolite yield. Therefore, it is ideal for therapeutic and nutritional purposes in aquaculture based on yield and quality of metabolites.