Efficient production of acetoin by fermentation using the newly isolated mutant strain Lactococcus lactis subsp. lactis CML B4

Abstract

Highlights A new strain, L. lactis CML B4, overproducing acetoin was obtained by mutagenesis.  This ldh-mutated strain showed reduced LDH and increased NOX activities.  Fermentations yielded >40 and 59 gL −1 acetoin in batch and fed-batch, respectively.  Maximum yields were close to 88% and productivities exceeded 2 gL −1 h −1 .  Potential use of the strain for industrial production of acetoin from bioresources. AbstractWith the aim of applying biotechnology to produce acetoin, a chemical that can be used as an aroma and as a building block for other compounds, several putative mutants with reduced lactic acid synthesis were obtained from a wild-type homolactic strain of L. lactis subjected to chemical mutagenesis. Among these mutants, a strain was isolated, CML B4, that showed reduced lactate dehydrogenase (LDH) and increased NADH oxidase (NOX) activities. Shaken flask cultures of this mutant strain mainly produced acetoin, increasing the levels produced compared to the wild-type strain by 15-fold. A point mutation detected in the ldh gene encoding LDH was probably the genetic defect responsible for this phenotype. In pH-controlled aerobic batch fermentation, the CML B4 strain produced more than 40 gL −1 acetoin, which was increased by up to 59 gL −1 in fed-batch fermentations, with yields close to 88 and 74%, respectively, and productivities exceeding 2 gL −1 h −1 . These results indicate that this strain could be used industrially as a cell factory for the production of acetoin from bioresources.

Effects of applying Lactobacillus helveticus H9 as adjunct starter culture in yogurt fermentation and storage

“…We detected over 100 different volatile metabolites, and gradual changes were observed in the volatile flavor compound profile throughout cold storage. Acetoin is a universal flavor substance present in many fermented dairy products; it has a mild creamy, slightly sweet, and butter-like flavor similar to that of diacetyl (Roncal et al, 2017). All L. helveticus H9-containing fermented milks had more acetoin than the control milk during cold storage.…”

From Waste to Taste—Efficient Production of the Butter Aroma Compound Acetoin from Low-Value Dairy Side Streams Using a Natural (Nonengineered) Lactococcus lactis Dairy Isolate

“…The productivity was also comparably high, even though 2.0 g/L/h has been reported when using a rich and expensive medium. 6 Considering that the fermentation substrate used in our study is based solely on a combination of waste streams, indicates that the solution has a great potential for industrial implementation.…”

Xylochemicals and where to find them

“…of sugars, [27,90] wood pyrolysis with addition of calcium carbonate [65] S HO OH OH glycerol byproduct of biodiesel production (50 wt%) [91][92] S OH Me Me O acetoin fmt. of sugars (>40 g/L) [93] P 1,3-butadiene (grain or potato) catalytic gas phase synthesis from ethanol [94] S Me HO 1-butanol ABE-fmt. of sugars (34 wt%) [27,74]…”