Volumetric oxygen transfer coefficient as fermentation control parameter to manipulate the production of either acetoin or D-2,3-butanediol using bakery waste.

The formation of either acetoin or D-2,3-butanediol (D-BDO) by Bacillus amyloliquefaciens cultivated on bakery waste hydrolysates has been evaluated in bioreactor cultures by varying the volumetric oxygen transfer coefficient (kLa). The highest D-BDO production (55.2 g L-1) was attained in batch fermentations with kLa value of 64 h-1. Batch fermentations performed at 203 h-1 led to the highest productivity (2.16 g L-1h-1) and acetoin production (47.4 g L-1). The utilization of bakery waste hydrolysate in fed-batch cultures conducted at kLa of 110 h-1 led to combined production of acetoin, meso-BDO and D-BDO (103.9 g L-1). Higher kLa value (200 h-1) resulted to 65.9 g L-1 acetoin with 1.57 g L-1h-1 productivity. It has been demonstrated that the kLa value may divert the bacterial metabolism towards high acetoin or D-BDO production during fermentation carried out in crude bakery waste hydrolysates.