Applied Microbiology

Biography

Biography: Sara Al-Araimi

Abstract

The world economy depends heavily on crude oil. With a conventional oil recovery process, only one-third of crude oil is extracted. Various technologies have been developed to maximize the recovery of oil resources from natural reservoirs. One of these is polymer technology that has been used in many oil fields around the world. The biopolymer pullulan, produced by A. mangrovei CBS 142331 showed high potential for EOR with the ability to increase oil recovery to a degree comparable to that achieved with many polymers used in oil fields around the world. However, pullulan is produced by the fungus simultaneously with a melanin pigment that is strongly attached to the polymer and considered an impurity for polymer flooding. The aim of this study is to improve and optimize the yield and purity of pullulan biopolymer and investigate the effect of different environmental factors on the expression of the genes responsible for pullulan and melanin synthesis. Under optimized conditions, that is, sucrose as the carbon source in the medium, a pH of 9, incubation at 25°C, and 250 rpm agitation and the fungus was able to produce 10 g/L of pullulan, which ultimately showed the ability to recover 36.7% of heavy crude oil. Melanin synthesis was strongly suppressed under nitrogen starvation where all the melanised cells transformed into transparent cells at the concentration of 30 g/L (NHâ‚„)â‚‚SOâ‚„. In fact, nitrogen starvation has a direct effect on the promoter of the polyketide synthase gene, the key enzyme involves in the melanin synthesis pathway. It was concluded that pullulan production by A. mangrovei CBS 142331 with limited melanin synthesis can be achieved by controlling the nitrogen concentration in the production media.