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.

Automated summary

The production of acetoin and D-BDO by Bacillus amyloliquefaciens cultivated on bakery waste hydrolysates can be influenced by varying the volumetric oxygen transfer coefficient (kLa). Batch fermentations with different kLa values were found to have significant impact on the production yields and rates, with fed-batch cultures at higher kLa values leading to combined production of acetoin, meso-BDO and D-BDO. The results suggest that manipulating the kLa value can redirect bacterial metabolism towards higher acetoin or D-BDO production during fermentation in crude bakery waste hydrolysates.