Development of a low cost culture medium for sakacin A production by L. sakei

A refined medium to enhance the antimicrobial activity of postbiotic produced by Lactiplantibacillus plantarum RS5

Postbiotic RS5, produced by Lactiplantibacillus plantarum RS5, has been identified as a promising alternative feed supplement for various livestock. This study aimed to lower the production cost by enhancing the antimicrobial activity of the postbiotic RS5 by improving the culture density of L. plantarum RS5 and reducing the cost of growth medium. A combination of conventional and statistical-based approaches (Fractional Factorial Design and Central Composite Design of Response Surface Methodology) was employed to develop a refined medium for the enhancement of the antimicrobial activity of postbiotic RS5. A refined medium containing 20 g/L of glucose, 27.84 g/L of yeast extract, 5.75 g/L of sodium acetate, 1.12 g/L of Tween 80 and 0.05 g/L of manganese sulphate enhanced the antimicrobial activity of postbiotic RS5 by 108%. The cost of the production medium was reduced by 85% as compared to the commercially available de Man, Rogosa and Sharpe medium that is typically used for Lactobacillus cultivation. Hence, the refined medium has made the postbiotic RS5 more feasible and cost-effective to be adopted as a feed supplement for various livestock industries.

Development of a Low-Cost and High-Efficiency Culture Medium for Bacteriocin Lac-B23 Production by Lactobacillus plantarum J23

At present, De Man, Rogosa and Sharpe (MRS) broth is the medium of choice for promoting bacteriocin production. However, this medium is expensive and not applicable for large-scale production. Therefore, a low-cost and high-efficiency culture medium for bacteriocin Lac-B23 production by Lactobacillus plantarum J23 was developed. First, the effects of the composition of MRS broth on bacteriocin Lac-B23 production and bacterial growth were researched by a one variable at a time approach. Then, a Plackett-Burman design was used to screen significant components for production. Finally, the steepest ascent and central composite designs were used to obtain an optimum medium. The final composition of the modified MRS was much simpler than MRS broth, and the modified MRS contained only glucose, yeast extract, dipotassium phosphate, manganese sulfate monohydrate, Tween 80 and sodium acetate anhydrous. The highest bacteriocin Lac-B23 production reached 2560 activity units (AU)/mL in the modified MRS, which is nine times higher than that in MRS broth (280 AU/mL). Meanwhile, the cost per liter of the modified MRS (8.56 Ren Min Bi (RMB)/L) is 34.70% the cost of MRS broth (13.11 RMB/L), and the cost per arbitrary units of bacteriocin Lac-B23 in the modified MRS is approximately fourteen times more convenient (3.34 RMB/106 AU) than in the MRS broth (46.82 RMB/106 AU).

From Cheese Whey Permeate to Sakacin A: A Circular Economy Approach for the Food-Grade Biotechnological Production of an Anti-Listeria Bacteriocin

Cheese Whey Permeate (CWP) is the by-product of whey ultrafiltration for protein recovery. It is highly perishable with substantial disposal costs and has serious environmental impact. The aim of the present study was to develop a novel and cheap CWP-based culture medium for Lactobacillus sakei to produce the food-grade sakacin A, a bacteriocin exhibiting a specific antilisterial activity. Growth conditions, nutrient supplementation and bacteriocin yield were optimized through an experimental design in which the standard medium de Man, Rogosa and Sharpe (MRS) was taken as benchmark. The most convenient formulation was liquid CWP supplemented with meat extract (4 g/L) and yeast extract (8 g/L). Although, arginine (0.5 g/L) among free amino acids was depleted in all conditions, its supplementation did not increase process yield. The results demonstrate the feasibility of producing sakacin A from CWP. Cost of the novel medium was 1.53 €/L and that of obtaining sakacin A 5.67 €/10⁶ AU, with a significant 70% reduction compared to the corresponding costs with MRS (5.40 €/L, 18.00 €/10⁶ AU). Taking into account that the limited use of bacteriocins for food application is mainly due to the high production cost, the obtained reduction may contribute to widening the range of applications of sakacin A as antilisterial agent.

Cellulose nanofiber (CNF)-sakacin-A active material: production, characterization and application in storage trials of smoked salmon

BACKGROUND

Sakacin-A due to its specific antimicrobial activity may represent a good candidate to develop active packaging solutions for food items supporting Listeria growth. In the present study a protein extract containing the bacteriocin sakacin-A, produced by Lactobacillus sakei Lb 706 in a low-cost culture medium containing deproteinized cheese whey, was adsorbed onto cellulose nanofibers (CNFs) to obtain an active material to be used as a mat (or a separator) in direct contact with foods.

RESULTS

The applied fermentation conditions allowed 4.51 g L^-1 of freeze-dried protein extract to be obtained, characterized by an antimicrobial activity of near 16 700 AU g^-1 , that was used for the preparation of the active material by casting. The active material was then characterized by infrared spectra and thermogravimetric analyses. Antimicrobial trials were carried out in vitro using Listeria innocua as indicator strain; results were also confirmed in vivo, employing smoked salmon fillets intentionally inoculated with Listeria innocua: its final population was reduced to about 2.5-3 Log cycles after 28 days of storage at 6 °C in presence of sakacin-A, compared with negative control mats produced without the bacteriocin extract.

CONCLUSION

This study demonstrates the possibility of producing an antimicrobial active material containing sakacin-A absorbed onto CNFs to decrease Listeria population in smoked salmon, a ready-to eat-food product. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Efficacy of Antimicrobial Agents for Food Contact Applications: Biological Activity, Incorporation into Packaging, and Assessment Methods: A Review

Interest in the utilization of antimicrobial active packaging for food products has increased in recent years. Antimicrobial active packaging involves the incorporation of antimicrobial compounds into packaging materials, with the aim of maintaining or extending food quality and shelf life. Plant extracts, essential oils, organic acids, bacteriocins, inorganic substances, enzymes, and proteins are used as antimicrobial agents in active packaging. Evaluation of the antimicrobial activity of packaging materials using different methods has become a critical issue for both food safety and the commercial utilization of such packaging technology. This article reviews the different types of antimicrobial agents used for active food packaging materials, the main incorporation techniques, and the assessment methods used to examine the antimicrobial activity of packaging materials, taking into account their safety as food contact materials.

Sakacin-A antimicrobial packaging for decreasing Listeria contamination in thin-cut meat: preliminary assessment

BACKGROUND

Minimally processed ready-to-eat products are considered a high-risk food because of the possibility of contamination with pathogenic bacteria, including Listeria monocytogenes from the animal reservoir, and the minimal processing they undergo. In this study, a sakacin-A anti-Listeria active package was developed and tested on thin-cut veal meat slices (carpaccio).

RESULTS

Enriched food-grade sakacin-A was obtained from a cell-free supernatant of a Lactobacillus sakei culture and applied (0.63 mg cm^-2 ) onto the surface of polyethylene-coated paper sheets to obtain an active antimicrobial package. The coating retained antimicrobial features, indicating that the process did not affect sakacin-A functionality, as evidenced in tests carried out in vitro. Thin-cut veal meat slices inoculated with Listeria innocua (a surrogate of pathogenic L. monocytogenes) were laid on active paper sheets. After 48 h incubation at 4 °C, the Listeria population was found to be 1.5 log units lower with respect to controls (3.05 vs 4.46 log colony-forming units (CFU) g^-1 ).

CONCLUSION

This study demonstrates the possibility of using an antimicrobial coating containing sakacin-A to inhibit or decrease the Listeria population in ready-to-eat products, thus lowering the risk of food-related diseases. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Fermentation factors influencing the production of bacteriocins by lactic acid bacteria: a review

Lactic acid bacteria (LAB) are the major interest in food industry primarily by virtue of their biopreservative properties.

Enhancement of BLIS production by Pediococcus acidilactici kp10 in optimized fermentation conditions using an artificial neural network

The present study was aimed at enhancing the production of BLIS produced byPediococcus acidilacticiKp10 through optimizing the fermentation parameters.

Recombinant production of hyperthermostable CelB from Pyrococcus furiosus in Lactobacillus sp

Lactic acid bacteria (LAB) are used widespread in the food industry as traditional starters for various fermented foods. For recombinant protein production, LAB would be superior with view from the food safety demands since most of them are Generally Recognized As Safe organisms. We investigated the two pSIP expression systems, pSIP403 and pSIP409 (Sørvig et al. 2005), to produce a hyper-thermophilic β-glycosidase (CelB) from Pyrococcus furiosus in Lactobacillus plantarum NC8 and Lactobacillus casei as hosts, respectively. Both lactobacilli harboring the pSIP409-celB vector produced active CelB in batch bioreactor cultivations (MRS medium) while the specific CelB activity of the cell free extract was about 44 % higher with L. plantarum (1,590 ± 90 nkat/mg(protein)) than with L. casei (1,070 ± 66 nkat/mg(protein)) using p-nitrophenyl-β-galactoside (pNPGal) as the substrate. A fed-batch bioreactor cultivation of L. plantarum NC8 pSIP409-celB resulted in a specific CelB activity of 2,500 ± 120 nkat ( pNPGal)/mg(protein) after 28 h. A repeated dosage of the inducer spp-IP did not increase the enzyme expression further. As alternative for the cost intensive MRS medium, a basal whey medium with supplements (yeast extract, Tween 80, NH(4)-citrate) was developed. In bioreactor cultivations using this medium, about 556 ± 29 nkat ( pNPGal)/mg(protein) of CelB activity was achieved. It was shown that both LAB were potential expression hosts for recombinant enzyme production. The pSIP expression system can be applied in L. casei.