초록
<P><B>Abstract</B></P> <P>With increasing demand for biodiesel, crude glycerol as a by-product in biodiesel production has been generated and oversupplied. This study, therefore, explored the pretreatment and a subsequent two-stage microbial system to convert crude glycerol into high value-added products: 1,3-propanediol (1,3-PDO) and polyhydroxyalkanoates (PHAs). After pretreatment, long chain fatty acids (LCFAs) could be effectively removed from crude glycerol to eliminate the inhibition effects on subsequent microbial process. In the anaerobic fermentation, when fed treated crude glycerol increased from 20 g/L to 100 g/L, 1,3-PDO yield decreased from 0.438 g/g to 0.345 g/g and accompanied carboxylic acids shifted from acetate and lactate dominant to lactate overwhelmingly dominant. Meanwhile, the relative abundance of <I>Clostridiales</I> sustained around 50% but <I>Enterobacteriales</I> increased from 19% to 53%. Further fed glycerol increase to 140 g/L resulted in severe substrate inhibition, which could be relieved by intermittent feeding. In aerobic process, glycerol anaerobic digestion effluent (ADE) was fed to the consortium of <I>Bacillus megaterium</I> and <I>Corynebacterium hydrocarbooxydans</I> for selectively consumption of carboxylic acids and residual glycerol from 1,3-PDO to produce PHAs as a secondary high value-added product. The consortium accumulated maximum 8.0 g/L poly (3-hydroxybutyrate) (PHB), and 1,3-PDO purity increased from initial 27.7% to almost 100% when fed with 100 g/L glycerol ADE. Overall, this study provided comprehensive and insightful information on microbial conversion of crude glycerol to high value-added products after pretreatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Up to140 g/L crude glycerol was applied to produce 1,3-PDO in anaerobic process. </LI> <LI> <I>Enterobacteriales</I> and <I>Clostridiales</I> were dominant in anaerobic process. </LI> <LI> Increasing fed glycerol resulted in less NADH pathways with lower 1,3-PDO yield. </LI> <LI> Retained 1,3-PDO and produced PHAs from other carbon sources by PHAs consortium. </LI> <LI> Indicated flexibility of selected PHAs consortium to 100 g/L glycerol ADE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>