Low-cost effective culture medium optimization for d-lactic acid production by Lactobacillus coryniformis subsp. torquens under oxygen-deprived condition

Alternative culture medium design for biomass production of autochthonous meat starter Latilactobacillus sakei sp. sakei ACU-2

The autochthonous strain Latilactobacillus sakei sp. sakei ACU-2 was selected as a meat starter culture for dry sausage production. Transferring this strain from laboratory scale to industry requires an increase in biomass production, while lowering process costs. In this study, a combination of techniques was applied in order to optimize the culture medium composition to enhance biomass production of L. sakei ACU-2. One variable at a time experiments, Plackett-Burman design, and mixture design were performed to fulfill the strain nutritional requirements. Eventually, the optimized formulation contained 19.46 g/L yeast extract; 8.28 g/L whey protein concentrate; 2.26 g/L soy peptone; 30 g/L cerelose; 1 g/L Tween 80; 5 g/L sodium acetate; 0.2 g/L magnesium sulfate and 0.05 g/L manganese sulfate. When L. sakei ACU-2 was cultivated in a bioreactor using the alternative medium, an enhancement of 75.5% of biomass production was achieved, in comparison to its growth in the commercial de Man, Rogosa, and Sharpe medium. Furthermore, a reduction of 62-86% of the cost was also attained. These results support a promising large-scale application of the designed medium for high biomass yields of the starter culture at minor costs.

A Natural Technology for Vacuum-Packaged Cooked Sausage Preservation with Potentially Postbiotic-Containing Preservative

In this study, a potentially postbiotic-containing preservative (PPCP) was produced in an axenic fermentation system with Lacticaseibacillus paracasei DTA 83 as a natural technology alternative for vacuum-packaged cooked sausage preservation. Cooked sausage-related microorganisms were obtained during the induced spoiling process in packages by pair incubation of sausages at different temperatures. The turbidity method was used to determine the microbiota susceptibility to PPCP. A controlled in situ design was performed by adding PPCP on the surface or to the mass of the sausages. Sodium lactate FCC85, which was used according to the manufacturer’s recommendation, was included in the design for comparison. The results revealed that PPCP was as efficient as FCC85, which indicates PPCP as a promising alternative to the use of natural technologies to preserve and develop functional cooked sausages. Moreover, a strategy to use preservatives in vacuum-packaged cooked sausages was presented: the concentration needed to achieve the total inhibition of the microbiota determined by an in vitro trial should be respected when adding PPCP on the sausages’ surface. When adding PPCP to the mass of the sausages, the concentration that showed a partial inhibition in vitro can also be applied in situ.

Growth Kinetics of Probiotic Lactobacillus Strains in the Alternative, Cost-Efficient Semi-Solid Fermentation Medium

The growing need for Lactobacillus bacteria usage in industry and the expending probiotic market led to a search for new cost-efficient fermentation media from which a high yield of these bacteria could be obtained. The following study aimed to elaborate cultivation medium, for Lactobacillus spp. growth, which main components would be wheat, maize, barley, and rye flours. The optimal temperature for Lactobacillus growth in new semi-solid fermentation (SSF) medium, water content, and pH of the medium were analyzed by the plate count method. It was established, that the highest bacteria counts were obtained from cultures conducted in the SSF medium with flours to water ratio of 1:1.5 with a natural pH of 6.0 at 37 °C. Subsequently, the growth kinetics of analyzed strains, in both MRS and the SSF media, were studied. The newly designed media contributed to the increased duration of selected Lactobacillus strains lag phase, which varied from 1.98 to 5.64; nevertheless, the maximum growth rate of the strains was two times higher in the SSF medium rather than in MRS, which also resulted in shorter generation time. The developed medium has the potential to become a new cost-efficient fermentation medium for Lactobacillus spp.

Functional Analysis of Sugars in Modulating Bacterial Communities and Metabolomics Profiles of Medicago sativa Silage

This study explored the effects of four sugar source treatments, including no sugar (CON), fructose (FRU), pectin (PEC), and starch (STA), on the microbiota and metabolome of alfalfa (Medicago sativa) silage. The bacterial community was determined via 16S rRNA gene sequencing. The metabolome was analyzed using ultra high-performance liquid chromatography tandem time-of-flight mass spectrometry (UHPLC/TOF-MS). After 60 days of fermentation, the pH values in FRU and PEC were lower than those in STA and CON. FRU had a greater lactic acid concentration compared to STA and CON. Weissella (47.44%) and Lactobacillus (42.13%) were the dominant species in all four groups. The abundance of Pediococcus was lower, and the abundance of Leuconostoc, Pantoea, and Microbacterium was higher, in FRU compared to CON. The abundance of norank_f__Bacteroidales_S24-7_group was higher, and the abundance of Turicibacter was lower, in both FRU and PEC than in CON. Leuconostoc was negatively correlated with the pH value, and Pediococcus was positively correlated with the pH value. No microbiomes were detected as discriminative features between STA and CON. The addition of FRU and PEC presented more peptides, such as Leu-Val-Thr, Leu-Phe, Ile-Pro-Ile, Val-Trp, and Ile-Leu-Leu but a lower abundance of metabolites for triterpene glycosides including sanchinoside B1, medicagenic acid, betavulgaroside IV, and prosapogenin compared to CON. The addition of PEC presented more phenyllactic acid compared to CON. Our study demonstrated that the addition of pectin and fructose improved the quality of alfalfa silage mainly by promoting Leuconostoc, Pantoea, and Microbacterium, and inhibiting Pediococcus in FRU, and promoting norank_f__Bacteroidales_S24-7_group and inhibiting Turicibacter in both FRU and PEC; this was due to altered metabolic profiles resulting from antifungal activity and decreased triterpene glycoside accumulation. This study improves our understanding of ensiling mechanisms related to the contributions of sugar.

Orange peels: from by-product to resource through lactic acid fermentation

BACKGROUND

Considering the large amounts of by-products derived from orange processing, which are generally discarded, the present study aimed to explore the feasibility of using orange peel for lactic acid production in solid state fermentation.

RESULTS

Different species of lactic acid bacteria were employed, singly and in co-culture, to evaluate their ability to ferment orange peel and produce lactic acid. Among the single cultures tested, Lactobacillus casei 2246 was the most efficient strain, reaching the highest concentration of lactic acid (209.65 g kg^-1 ) and yield (0.88 g g^-1 ). The use of Lactobacillus plantarum 285 and Lactobacillus paracasei 4186 in co-culture produced a comparable amount of lactic acid, showing a better performance than the same strains in single cultures.

CONCLUSION

Orange peels represent a suitable raw material for solid state fermentation employing lactic acid bacteria. Lactic acid was obtained that consumed the most of sugars available, leading to high yields. Despite all the strains tested showing the same growth ability, different peculiarities in lactic acid production were revealed, dependent on the species/strains, suggesting the relevance of strain selection. © 2019 Society of Chemical Industry.