Process strategies for enhanced production of 1,3-propanediol by Lactobacillus reuteri using glycerol as a co-substrate

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.

Production of 1,3-propanediol by Lactobacillus diolivorans from agro-industrial residues and cactus cladode acid hydrolyzate

This study evaluated the bioproduction of 1,3-propanediol by Lactobacillus diolivorans in the medium based on agro-industrial residues and vegetal biomass substituting the MRS medium components. It was performed on a set of acid treatments and batch fermentations assays with crude glycerol (TCG) from biodiesel production, corn steep liquor (CSL), and cactus cladode hydrolyzate (CCH). Firstly, it was carried out on batch fermentation with different pure glycerol concentrations in MRS medium which was carried out, and the best condition achieved 4.66 g/L and 0.61 g/g of 1,3-PDO production and yield, respectively. Then, the TCG was evaluated, and a discrete increase of 1,3-PDO was observed. The replacement of the MRS medium nutrients by CLS was assessed, at different concentrations, for bacteria growth, and 5% of CLS reproduced the same biomass formation compared to the bacteria growth in MRS medium. It was also added cactus cladode hydrolyzate as the only sugar source, which showed a 1,3-PDO production close to the medium with pure glucose. Finally, a B-complex vitamin was added to the batch fermentation medium composed of TCG, CLS, and CCH, replacing all the costly MRS components. In this medium, the production of 1,3-propanediol was 6.57 g/L with a yield of 0.75 g/g. It means an increment of 29% and 19%, respectively, compared to MRS medium. Therefore, the combination of treated crude glycerol, corn steep liquor, and cactus cladode hydrolyzate has excellent potential for 1,3-PDO production by L. diolivorans.

SUSU FERMENTASI DENGAN BIJI NANGKA SEBAGAI PREBIOTIK

Jackfruit seeds (Artocarpus heterophyllus Lam.) contain dietary fiber, thus it is potential as prebiotic to be used in fermented milk drink. This research aimed to obtain the fermented milk composition made from fresh milk and jackfruit seed flour containing active lactic acid bacteria (LAB), preferred hedonic level and to identify the chemical properties of the resulting fermented milk. Variables of this research were the jackfruit seed flour concentrations of 4, 5, 6% (w/v) and two LAB used (Lactobacillus plantarum and Lactobacillus brevis). The composition was selected based on the viable number of LAB, pH value, and sensory quality. The selected composition was the fermented milk made of fresh milk and 4% (w/v) jackfruit seed flour and L. brevis. The viable number of LAB of the fermented milk was 10.59 log CFU/mL. The sensory quality of the fermented milk was neutral until rather preferred for color, flavor, taste, texture, and overall. The chemical contents (%b/b) of product was 78.16% of moisture content, 2.34% of ash content, 2.85% of fat content, 3.15% of protein content, 13.51% of carbohydrate content, and 1.73% of lactic acid content.

Rapid determination of 1,3-propanediol in fermentation process based on a novel surface-enhanced Raman scattering biosensor

The production of 1,3-propanediol (1,3-PDO) is an important fermentation process. However, 1,3-PDO could not be distinguished separately and efficiently in fermentations previously because it has a highly similar molecular structure to the feedstock glycerol (GLY) and by-product lactic acid (Lac), which leads to the difficulty of quantification. In this paper, a low-cost and environmentally friendly biosensor based on surface-enhanced Raman scattering (SERS) technique was developed. Using it, the concentration of 1,3-PDO and Lac in a fermentation solution can be determined directly from their respective characteristic peaks in Raman spectroscopy. Moreover, by analyzing the respective contributions of 1,3-PDO, Lac, and GLY to the integrated intensities of the 2920 cm^-1 Raman peak common to these three substances, the concentration of GLY could also be quantified. SERS study on various 1,3-PDO:GLY and Lac:GLY molar ratios were conducted to establish the proportional relationships of these compounds by analyzing the relationship between the concentration and the Raman peak intensities. The 1,3-PDO:Lac:GLY with serial concentration gradient was carried out to verify the relationship between the concentration and the Raman peak intensities by the high-performance liquid chromatography (HPLC) with relative deviations <25%. Concentrations of 1,3-PDO and Lac as low as 1 g/L and concentration of GLY as low as 4 g/L were analyzed to determine the limit of detection. Therefore, this new method allows the rapid quantification of 1,3-PDO, Lac and GLY concentrations on a SERS-based biosensor.

Lactobacillus reuteri growth and fermentation under high pressure towards the production of 1,3-propanediol

Lactobacillus reuteri is a lactic acid bacterium able to produce several relevant bio-based compounds, including 1,3-propanediol (1,3-PDO), a compound used in food industry for a wide range of purposes. The performance of fermentations under high pressure (HP) is a novel strategy for stimulation of microbial growth and possible improvement of fermentation processes. Therefore, the present work intended to evaluate the effects of HP (10-35 MPa) on L. reuteri growth and glycerol/glucose co-fermentation, particularly on 1,3-PDO production. Two different types of samples were used: with or without acetate added in the culture medium. The production of 1,3-PDO was stimulated at 10 MPa, resulting in enhanced final titers, yields and productivities, compared to 0.1 MPa. The highest 1,3-PDO titer (4.21 g L^-1) was obtained in the presence of acetate at 10 MPa, representing yield and productivity improvements of ≈ 11 and 12%, respectively, relatively to the same samples at 0.1 MPa. In the absence of acetate, 1,3-PDO titer and productivity were similar to 0.1 MPa, but the yield increased ≈ 26%. High pressure also affected the formation of by-products (lactate, acetate and ethanol) and, as a consequence, higher molar ratios 1,3-PDO:by-products were achieved at 10 MPa, regardless of the presence/absence of acetate. This indicates a metabolic shift, with modification of product selectivity towards production of 1,3-PDO. Overall, this work suggests that HP can be a useful tool to improve of 1,3-PDO production from glycerol by L. reuteri, even if proper process optimization and scale-up are still needed to allow its industrial application. It also opens the possibility of using this technology to stimulate other glycerol fermentations processes that are relevant for food science and biotechnology.

Multi-modular engineering of 1,3-propanediol biosynthesis system in Klebsiella pneumoniae from co-substrate

1,3-Propanediol (1,3-PDO) is a monomer for the synthesis of various polyesters. It is widely used in industries including cosmetics, solvents, and lubricants. Here, the multi-modular engineering was used to improve the concentration and tolerance of 1,3-PDO in Klebsiella pneumoniae. Firstly, the concentration of 1,3-PDO was increased by 25 %, while the concentrations of by-products were reduced considerably through one-step evolution which focused on the glycerol pathway. In addition, the 1,3-PDO tolerance was improved to 150 g L^-1. Secondly, co-substrate transport system was regulated, and the 1,3-PDO concentration, yield, and productivity of the mutant were improved to 76.4 g L^-1, 0.53 mol mol^-1, and 2.55 g L^-1 h^-1, respectively. Finally, NADH regeneration was introduced and the recombinant strain was successfully achieved with a high productivity of 2.69 g L^-1 h^-1. The concentration and yield of 1,3-PDO were also improved to 86 g L^-1 and 0.59 mol mol^-1. This strategy described here provides an approach of achieving a superior strain which is able to produce 1,3-PDO with high productivity and yield.

Biological valorization of pure and crude glycerol into 1,3-propanediol using a novel isolate Lactobacillus brevis N1E9.3.3

The aim of the study was to evaluate a novel onsite enrichment approach to isolate a crude glycerol utilizing facultative anaerobic bacteria. An onsite enrichment in natural conditions resulted an isolate, Lactobacillus brevis N1E9.3.3, that can utilize glycerol and produce 1,3-propanediol with a yield of 0.89g1,3-PDO/gGlycerol and productivity of 0.78g1,3-PDO/l/h at pH-8.5 under anaerobic conditions. Batch fermentation experiments with glycerol-glucose co-fermentation strategy was carried out to evaluate the production of 1,3-propanediol and other byproducts. The effect of other carbon sources as co-substrate was also evaluated. At the optimized condition, 18.6g/l 1,3-propanediol was monitored when biodiesel industry generated crude glycerol and 2.5% glucose were used as the substrate.

1,3-Propanediol production from glycerol with a novel biocatalyst Shimwellia blattae ATCC 33430: Operational conditions and kinetics in batch cultivations

Shimwellia blattae ATCC 33430 as biocatalyst in the conversion of 1,3-propanediol from glycerol is herein evaluated. Several operational conditions in batch cultivations, employing pure and raw glycerol as sole carbon source, were studied. Temperature was studied at shaken bottle scale, while pH control strategy, together with the influence of raw glycerol and its impurities during fermentation were studied employing a 2L STBR. Thereafter, fluid dynamic conditions were considered by changing the stirring speed and the gas supply (air or nitrogen) in the same scale-up experiments. The best results were obtained at a temperature of 37°C, an agitation rate of 200rpm, with free pH evolution from 6.9 and subsequent control at 6.5 and no gas supply during the fermentation, employing an initial concentration of 30g/L of raw glycerol. Under these conditions, the biocatalyst is competitive, leading to results in line with other previous works in the literature in batch conditions, reaching a final concentration of 1,3-propanediol of 13.84g/L, with a yield of 0.45g/g and a productivity of 1.19g/(Lh) from raw glycerol.