Application of foaming capacity as response value in optimization of biosurfactant production

Equipment for determination of surface tension (ST) which is the response value often used during biosurfactant optimization are not readily available in many laboratories. Foaming capacity (FC) was thus investigated as response value during biosurfactant optimization. Thirteen variations of glycerol-mineral salts medium were used to culture Pseudomonas sp. for biosurfactant production and optimization. Variations in the medium were based on pH, carbon-nitrogen (C-N) and carbon-phosphorus (C-P) ratio. Inoculated media were incubated at ambient temperature with orbital shaking at 150 rpm for four days. FC of the media were then determined and fitted using a polynomial model so as to obtain a prediction profile. The prediction profile was used to determine the combination of C-N ratio, C-P ratio, and pH that will lead to the highest FC. This combination was used in another experimental run for biosurfactant production, and at the end the culture was screened for biosurfactant activity. The results obtained showed that foaming was achieved in selected experimental runs, and the model for the prediction profile was worked out to be Y = -513.03 + 103.3804 X1 + 2.1211 X2 + 16.2848 X3 – 0.1108X1X2 – 0.3656 X1X3 – 0.0339X2X3 – 6.1730 X12 – 0.0099 X22 – 0.4432 X32. From the prediction profiles it was seen that the highest FC (32.04%) was achievable at combination of pH 7.0, C-N 40, and C-P 13. Biosurfactant activity of the culture with optimized combination showed that ST reduced from 56.43 to 35.28 mN.m-1. It is concluded that FC can be used in place of ST during biosurfactant optimization procedures.