The Effects of Various Immobilization Matrices on Biosurfactant Production using Hydrocarbon (HC)-Degrading Marine Bacteria via the Entrapment Technique

Bioavailability and environmental stress are problems affecting Poly Aromatic Hydrocarbons (PAH) biodegradation. This study aims to overcome the effect of PAH bioavailability via biosurfactant production and the effect of environmental stresses via using different immobilization matrices. Three different PAH bacterial degraders (A2, P5 and N7) were immobilized in different immobilization matrices. The immobilization matrices used in this investigation were: ca-alginate, agar-agar and agarose. RAPD-PCR, plasmid profile and 16S rRNA sequencing methods were used to identify and group the bacterial isolates. The production of biosurfactant was detected using the methylene blue analysis procedure. The results indicated that P5 and N7 isolates preferred the alginate matrix compared to the agar and agarose matrices, where biosurfactant production was 136 and 165.5 mg L-1 for both isolates, respectively. However, the A2 isolate produced a higher biosurfactant concentration (132.4 mg L-1) when grown on agarose. The preferred matrices for the three isolates were different in the presence of hydrocarbons. The A2 and P5 isolates preferred agar as the best matrix for biosurfactant production. On the other hand, the free cells of the N7 isolate produced the highest concentration of biosurfactant compared to immobilized cells. The overall results of this study showed that the type of preferred immobilization matrix depends on the used carbon source; where, in general, calcium alginate was preferred at the presence of glucose while agar was preferred at the presence of hydrocarbons.