Bioprocess development for (2R,3R)‐butanediol and acetoin production using very high polarity cane sugar and sugarcane molasses by a Bacillus amyloliquefaciens strain

Abstract

BACKGROUND: Efficient production of (2R,3R)-2,3-butanediol (BDO) and acetoin using the GRAS strain Bacillus amyloliquefaciens from very high polarity (VHP) cane sugar and sugarcane molasses could lead to the development of a sustainable industrial process. RESULTS:The effect of initial substrate concentration, nitrogen source, temperature, inoculum size and pH were evaluated in shake flask cultures. Batch bioreactor cultures showed that (2R,3R)-BDO production (up to 28 g L −1 ) with high yield (up to 0.43 g g −1 ) and productivity (up to 0.93 g L −1 h −1 ) was favored at low k L a values (17-49 h −1 ). Increasing k L a values (63-104 h −1 ) initiated acetoin production (up to 25.6 g L −1 ) with yields up to 0.4 g g −1 and productivities up to 1.42 g L −1 h −1 . Fed-batch fermentation carried out at k L a value of 49 h −1 with VHP cane sugar resulted in mixed production (127.3 g L −1 ) of (2R,3R)-BDO, (2R,3S)-BDO and acetoin at 122 h with high yield (0.50 g g −1 ) and productivity (1.04 g L −1 h −1 ). In a similar fed-batch fermentation with sugarcane molasses, mainly (2R,3R)-BDO production (48.7 g L −1 with purity of 87.8%) was achieved at 59 h with yield of 0.4 g g −1 and productivity of 0.83 g L −1 h −1 . At 130 h, (2R,3R)-BDO was converted mainly into acetoin (55.4 g L −1 ). CONCLUSION:This study demonstrates that k L a manipulation could be used in batch cultures to divert the bacterial metabolism towards either (2R,3R)-BDO or acetoin production. Fed-batch cultures with sugarcane molasses could lead to either (2R,3R)-BDO or acetoin production with negligible by-product formation.

Production of poly‐gamma‐glutamic acid and spore formation in Bacillus velezensis 83 are affected by acidic growing conditions and glucose uptake rate

“…22 This behavior was boosted under acidic conditions due that acetate was not detected on glucose consuming phase in batch cultivations, in contrast to neutral environments where acetate was produced and subsequently switched to acetoin and butanediol synthesis. [42][43][44] Higher acetoin and butanediol concentrations at pH 5 agrees with other studies that have reported upregulation of anabolic pathways for acetoin and butanediol production in acidic environments. 45 Consumption of acetoin and butanediol after glucose exhaustion could be related with a decrease in expression of systems required for catabolism of these compounds.…”

Whole sugar 2,3-butanediol fermentation for oil palm empty fruit bunches biorefinery by a newly isolated Klebsiella pneumoniae PM2

“…inferring the reversible action of 2,3-BDO to acetoin upon glucose depletion in the broth (Maina et al, 2019). As shown in Fig.…”

“…Concomitantly, acetoin accumulation increased up to 6.84±0.27 g/L after 2,3-BDO concentration reached a plateau, indicating the reversible action of butanediol dehydrogenase for NAD + /NADH redox balance (Maina et al, 2019). Ethanol (6.7±0.33 g/L), succinic acid…”

Prospects on bio-based 2,3-butanediol and acetoin production: Recent progress and advances

“…A simple oxygen supply method based on constant agitation speed has been extensively used for BDO production. High agitation rates stimulate bacterial growth, acetoin and acetate accumulation leading to decreased BDO yields, whereas low agitation rate favor BDO and byproduct (namely succinate, lactate and ethanol) formation (Priya et al, 2016;Maina et al, 2019a). Cho et al (2015) reported BDO and acetoin production of 118.5 g L -1 and 42.1 g L -1 , respectively at 400 rpm with low by-product accumulation.…”