Microbial selection strategies for polyhydroxyalkanoates production from crude glycerol: Effect of OLR and cycle length

Crude glycerol from biodiesel manufacture can be used as carbon source for microbial fermentations. The production of polyhydroxyalkanoates by manipulating the Sequencing Batch Reactor (SBR) selection stage of microbial mixed cultures (MMC) using high organic loading rates (OLR, 50C mM/day) and different cycles lengths (6, 12 and 24 h) were optimized. Batch-production of polyhydroxybutyrate (PHB) presented an accumulation capacity in the high range (0.44 g/g) after 3 pulses of 50C mM, with a final content of 59% PHB/wt., for the culture selected with 50C mM/day and a 24 h cycle length. These values were in the range to those obtained with pure cultures and higher than the ones for MMC. With this strategy three main advantages in terms of the PHA production can be considered: utilization of a real waste without the resort to pure microbial cultures and a pre-fermentation step, consolidating the role of MMC in the valorisation of complex wastes/by-products.