Bacteriocins to the rescue of silage

Project entitled:

Bacteriocins: A natural approach to controlling thermoduric bacteria in silage

Highlights

• Sporulated thermoduric bacteria in silage is one of the major problems the dairy industry faces. These bacteria can be found in fermented dairy products, causing major defects in taste and texture, and considerable economic losses.
• In this project, various natural ingredients derived from lactic bacteria bacteriocins will be developed, characterized, and tested for their effectiveness in controlling Clostridium bacteria in silage.
• Different Clostridium species have already been isolated and characterized from butyric silage on four farms in Quebec.
• Processes have been developed for the production and purification of reuterin, pediocin, bactofencin, and nisin, four antimicrobials produced by lactic bacteria. The inhibitory activity against Clostridium of these bacteriocins will be evaluated in vitro and in model silos.
• The proposed approach in this project will be a promising new strategy for controlling thermoduric bacteria in silage and preventing the contamination of dairy products and their associated losses.

Objectives

1. Isolate and characterize Clostridium strains from silage produced in Quebec.
2. Produce and purify various lactic acid bacteria bacteriocins, namely, nisin A, nisin Z, pediocin, bactofencin and reuterin.
3. Evaluate the in vitro inhibitory activity of different bacteriocins alone or in combination against different Clostridium isolates.
4. Demonstrate the inhibitory activity of bacteriocin formulations against Clostridium and measure their impacts on silage quality and stability.

Results and potential benefits

This project will generate unique scientific data on the potential of natural antimicrobial compounds (bacteriocins) in controlling undesirable flora in silage. Such products meet a critical need of dairy farmers and processors, where controlling the microbiological quality of silage and forage milk has become a major issue because of thermoduric bacteria. A unique collection of Clostridium isolates was collected from silage. The characterization of these strains will help to better understand their role in the alteration of Quebec-produced silage and fermented dairy products. Processes will be developed for the production and purification of various natural antimicrobials (reuterin, pediocin, and nisin). Their inhibitory activities against Clostridium isolates will be determined in vitro as well as in silage.
The development of these antimicrobial ingredients will control the thermoduric bacteria in silage and thus reduce the economic losses associated with undesirable fermentations, which affect up to 12% of the silage produced. It would also improve the productivity of dairy cattle and provide better milk with a higher microbiological quality. Among other things, reducing the incidence of butyric sporulate bacteria would reduce the taste and texture defects caused by these bacteria and thus limit the economic losses resulting from them.
Innovative aspects
• The project takes an original approach based on the use of natural, high-value-added food-grade antimicrobial compounds.
• The antimicrobial activity of these compounds, alone or in synergistic combinations, against non-sporulated and sporulated thermoduric bacteria will be characterized and demonstrated in vitro under real conditions of silage production. Particular attention will be given to the Clostridium genus, with a focus on C. tyrobutyricum.
• The proposed approach to improving the nutritional quality of silage can also be applied in other stages of the milk and dairy production chain.

Professionals trained

Liya Zhang is currently a postdoctoral fellow for the project.
A PhD student, Vahideh Vahdatmanesh, was recruited. She will begin her doctoral studies in the near future. A master’s student will also be recruited for the various tests on silage.