Promoting Magnusiomyces spicifer AW2 Cell-Bound Lipase Production by Co-culturing with Staphylococcus hominis AUP19 and Its Application in Solvent-Free Biodiesel Synthesis.

Yeast-bacterium interaction has recently been investigated to benefit the production of cell-bound lipases (CBLs). Staphylococcus hominis AUP19 supported the growth of Magnusiomyces spicifer AW2 in a palm oil mill effluent (POME) medium to produce CBLs through a bioremediation approach, including oil and grease (O&G) and chemical oxygen demand (COD) removals. This research used the yeast-bacterium co-culture to optimize CBLs and cell biomass (CBM) productions through bioremediation using the statistical Plackett-Burman design and response surface methodology-central composite design. The CBLs were finally applied in biodiesel synthesis. The CBM of 13.8 g/L with CBLs activity at 3391 U/L was achieved after incubation at room temperature (RT, 30 ± 2 °C) for 140 h in 50% POME medium, pH 7.0, containing 1.23% (w/v) ammonium sulfate. Bacterium promoted yeast growth to achieve bioremediation with 87.9% O&G removal and 84.5% COD removal. Time course study showed that the CBLs activity was highest at 24 h cultivation (4103 U/L) and retained 80% and 60% of activities at 4 °C and RT after 5 weeks of storage. The CBLs application successfully yielded 77.3% biodiesel from oleic acid (esterification) and 86.4% biodiesel from palm oil (transesterification) within 72 h in solvent-free systems. This study highlights that yeast-bacterium co-culture and POME should receive more attention for potential low-cost CBLs production through bioremediation, i.e., O&G and COD removals, while the CBLs as biocatalysts are promising for significant contribution to an effective strategy for economic green biodiesel production.