Semicarbazide-functionalized resin as a new scavenger for in situ recovery of 3-hydroxypropionaldehyde during biotransformation of glycerol by Lactobacillus reuteri

Application of the Reuterin System as Food Preservative or Health-Promoting Agent: A Critical Review

The reuterin system is a complex multi-component antimicrobial system produced by Limosilactobacillus reuteri by metabolizing glycerol. The system mainly includes 3-hydroxypropionaldehyde (3-HPA, reuterin), 3-HPA dimer, 3-HPA hydrate, acrolein and 3-hydroxypropionic acid, and has great potential to be applied in the food and medical industries due to its functional versatility. It has been reported that the reuterin system possesses regulation of intestinal flora and anti-infection, anti-inflammatory and anti-cancer activities. Typically, the reuterin system exerts strong broad-spectrum antimicrobial properties. However, the antimicrobial mechanism of the reuterin system remains unclear, and its toxicity is still controversial. This paper presents an updated review on the biosynthesis, composition, biological production, antimicrobial mechanisms, stability, toxicity and potential applications of the reuterin system. Challenges and opportunities of the use of the reuterin system as a food preservative or health-promoting agent are also discussed. The present work will allow researchers to accelerate their studies toward solving critical challenges obstructing industrial applications of the reuterin system.

The Biocatalytic Production of 3-Hydroxypropionaldehyde and Evaluation of Its Stability

3-Hydroxypropionaldehyde (3-HPA, reuterin) is a broad-spectrum natural antimicrobial agent used in the food industry and other fields. The low yield from the industrial production of 3-HPA using Lactobacillus reuteri and the spontaneous conversion of 3-HPA to acrolein have limited its more widespread use. We isolated L. reuteri BR201 as a biocatalyst for 3-HPA production and confirmed the effect of each factor in the two-step procedure for 3-HPA bioconversion. After initial cultivation for 8 h (late exponential phase), this isolate produced 378 mM of 3-HPA in 1 h at a concentration of OD600 nm 100, 30 °C, and an initial glycerol concentration of 500 mM. This is the highest reported biocatalytic yield of 3-HPA from a glycerol aqueous solution without additives. We confirmed that 4 mM of 3-HPA had antimicrobial activity against five pathogens. The degradation of 3-HPA to acrolein was greater at high temperatures, and there was little degradation when 3-HPA was maintained at 4 °C for 4 weeks. Our results may be useful for future applications of 3-HPA.

Crosslinked, cryostructured Lactobacillus reuteri monoliths for production of 3-hydroxypropionaldehyde, 3-hydroxypropionic acid and 1,3-propanediol from glycerol

Crosslinked, cryostructured monoliths prepared from Lactobacillus reuteri cells were evaluated as potential immobilized whole-cell biocatalyst for conversion of glycerol, to potentially important chemicals for the biobased industry, i.e. 3-hydroxypropionaldehyde (3HPA), 3-hydroxypropionic acid (3HP) and 1,3-propanediol (1,3PDO). Glutaraldehyde, oxidized dextran and activated polyethyleneimine/modified polyvinyl alcohol (PEI/PVA) were evaluated as crosslinkers; the latter gave highly stable preparations with maintained viability and biocatalytic activity. Scanning electron microscopy of the PEI/PVA monoliths showed high density of crosslinked cells with wide channels allowing liquid flow through. Flux analysis of the propanediol-utilization pathway, incorporating glycerol/diol dehydratase, propionaldehyde dehydrogenase, 1,3PDO oxidoreductase, phosphotransacylase, and propionate kinase, for conversion of glycerol to the three chemicals showed that the maximum specific reaction rates were -562.6, 281.4, 62.4 and 50.5mg/g_CDWh for glycerol consumption, and 3HPA (extracellular), 3HP and 1,3PDO production, respectively. Under optimal conditions using monolith operated as continuous plug flow reactor, 19.7g/L 3HPA was produced as complex with carbohydrazide at a rate of 9.1g/Lh and a yield of 77mol%. Using fed-batch operation, 1,3PDO and 3HP were co-produced in equimolar amounts with a yield of 91mol%. The monoliths embedded in plastic carriers showed high mechanical stability under different modes in a miniaturized plug flow reactor.

Efficient poly(3-hydroxypropionate) production from glycerol using Lactobacillus reuteri and recombinant Escherichia coli harboring L. reuteri propionaldehyde dehydrogenase and Chromobacterium sp. PHA synthase genes

Poly(3-hydroxypropionate), P(3HP), is a polymer combining good biodegradability with favorable material properties. In the present study, a production system for P(3HP) was designed, comprising conversion of glycerol to 3-hydroxypropionaldehyde (3HPA) as equilibrium mixture with 3HPA-hydrate and -dimer in aqueous system (reuterin) using resting cells of native Lactobacillus reuteri in a first stage followed by transformation of the 3HPA to P(3HP) using recombinant Escherichia coli strain co-expressing highly active coenzyme A-acylating propionaldehyde dehydrogenase (PduP) from L. reuteri and polyhydroxyalkanoate synthase (PhaCcs) from Chromobacterium sp. P(3HP) content of up to 40% (w/w) cell dry weight was reached, and the yield with respect to the reuterin consumed by the cells was 78%. Short biotransformation period (4.5h), lack of additives or expensive cofactors, and use of a cheap medium for cultivation of the recombinant strain, provides a new efficient and potentially economical system for P(3HP) production.