Low-cost production of cell-bound lipases by pure and co-culture of yeast and bacteria in palm oil mill effluent and the applications in bioremediation and biodiesel synthesis

Two bacterial and six yeast strains capable of lipase production were investigated for their extracellular lipase (ECL), cell-bound lipase (CBL), and growth profile in basal standard medium (BSM) and the low-cost palm oil mill effluent (POME) media. The yeast Magnusiomyces spicifer AW2 and bacteria Staphylococcus hominis AUP19 were selected and further employed to explore their survivability, lipase activity, and cell biomass production in various POME concentrations. It was revealed that diluted POME 1:1 at pH 7.0 was suitable for yeast and bacterial performance. Furthermore, the development of co-culture between yeast and bacteria was performed by mixing them at a ratio of 1:1. The synthetic co-culture system was successful in improving CBL activity to 3860 U/L. The bioremediation parameter, i.e., oil and grease (O&G) removal, was efficiently achieved 1.1-fold higher than yeast alone and bacterial monoculture at 80.1 +/- 1.3%. At the same time, COD removal was highest with the co-culture treatment of 75.9 +/- 2.8%, indicating 1.3-fold more effective than yeast monoculture and 1.4-fold better than single bacterial form. The mixed cells of two strains effectively improved biodiesel production from oleic acid of 73.5 +/- 3.3% and palm oil of 82.5 +/- 0.3% under solvent-free conditions for 72-h reactions at room temperature (30 +/- 2 degrees C), indicating a promising prospect of a combined approach of POME treatment and valorization.