Enhancement of Biosurfactant Production from Pseudomonas cepacia CCT6659 Through Optimisation of Nutritional Parameters Using Response Surface Methodology

Abstract

The aim of the present study was to optimise the production of a biosurfactant by a new strain of Pseudomonas cepacia CCT6659 with aid of a combination of central composite rotatable design (CCRD) and response surface methodology (RSM). The factors selected for optimisation of the growth conditions were canola waste frying oil, corn steep liquor and NaNO3 substrate concentrations. Surface tension was chosen as the response variable. All factors studied were important within the ranges investigated. The empirical forecast model developed through RSM regarding effective nutritional factors was adequate for explaining 89 % of the variation observed in biosurfactant production. Maximal reduction in surface tension of 26 mN m–1 was obtained under the optimal conditions of 2 % waste frying oil, 3 % corn steep liquor and 0.2 % NaNO3. The accumulation of isolated biosurfactant increased from 2 g L–1 to 8.0 g L–1 under these conditions, demonstrating that the factorial design is adequate for identifying the optimal conditions for biosurfactant production.

Response Surface Methodology for Optimizing the Production of Biosurfactant by Candida tropicalis on Industrial Waste Substrates

“…On the other hand, the use of corn steep liquor as the nitrogen source for biosurfactant produced by microorganisms has been widely studied (Luna et al, 2013; Silva et al, 2013, 2014a; Campos et al, 2014; Santos et al, 2014). In a study by Luna et al (2013), the utilization of corn steep liquor as low cost constituent to C. sphaerica growth resulted in reducing the surface tension of cell-free broth to 25 mNm −1 and biosurfactant yield was 9 gL −1 .…”

“…The organic phase was removed and the operation was repeated twice. The pooled product from organic phase was dried in an oven until complete evaporation of the solvent at 80°C to a constant weight (Silva et al, 2013). …”

“…Industrial wastes have attracted considerable interest from researchers as low-cost substrates for this purpose, as the substrate generally accounts for up to 50% of the final production cost (Das et al, 2009; Rufino et al, 2014). Residues, such as corn steep liquor (Silva et al, 2013), glycerol (Silva et al, 2010), clarified cashew apple juice (Oliveira and Garcia-Cruz, 2013), vinasse (Oliveira et al, 2013), cassava wastewater (Barros et al, 2008), soybean oil refinery residue (Luna et al, 2011a), ground-nut oil refinery residue (Sobrinho et al, 2008), animal fat (Santos et al, 2013), vegetable fat (Gusmão et al, 2010), waste frying oil (Batista et al, 2010), and molasses (Santos et al, 2010) have demonstrated excellent results when used for biosurfactant production by microorganisms.…”

“…Response surface methodology (RSM) has been effectively employed to reduce the production cost of biosurfactants through the selection of balanced proportions of the constituents of the culture medium and the optimization of culture conditions (Najafi et al, 2011; Kim and Kim, 2013; Silva et al, 2013; Kumar et al, 2015). RSM constitutes a collection of statistical techniques for designing experiments, building models, simultaneously evaluating the effects of factors and establishing optimum conditions.…”

“…A central composite rotational design (CCRD) is used with RSM to examine the relationship between one or more response variables and set of quantitative experimental factors (Kim and Kim, 2013). As the correlation between the response and independent variables is generally unknown at the onset of a process, the first step in RSM is to approximate the function (response) by analyzing the factors (independent variables) (Najafi et al, 2010; Silva et al, 2013). …”