Automated colony picking in precision probiotics?

Summary

There are many applications of Lactobacillus in the agricultural industry, from improving animal health, to increasing the quality of the food on our plates. Due to the vast variety of species of Lactobacillus, identifying production strains for animal feed or for human probiotics can be a long and complex process. Colony pickers can be a useful way to speed up screening assays and identify antimicrobial properties such as through measuring zones of inhibition.

What is Lactobacillus?

Lactobacillus is commonly present in probiotics, providing beneficial effects for humans and animals. The Lactobacillus genera contain Lactobacillus bulgaricus, rhamnosus, sakei and at least 258 other species [1]. Using Lactobacillus in agriculture has gained worldwide attention over the last decade due to its potential in increasing the welfare of animals and improving productivity in food production. Applications of lactobacilli include pre-harvest in animal welfare; and post-harvest and processing procedures to increase food safety and reduce the risk of contaminants before consumption.

Lactobacillus in agriculture

Lactobacilli in probiotics reduces pathogenic organisms entering the food chain, especially in emerging nations where there is distrust in the safety of the food produced [2].

In poultry, Lactobacillus strains have been identified to inhibit salmonella colonisation reducing risk of spreading infection and also reducing risk to the end consumer [3].

In research, colony pickers can be used to pick and identify production strains, PIXL has previously been used to identify strains of lactobacilli picked from MRS agar, to then be cultured in bioreactors to be supplied as probiotics for chickens.

Focus on probiotics

Probiotics containing lactobacilli have an antimicrobial effect on E.coli. Lactobacillus rhamnosus has been shown to be effective in reducing pathogenic E.coli when given to mice in fermented milk [4]. L. rhamnosus also increases production of cytokines, working as an immunostimulatory agent [5]. PIXL can be used to screen strains, such as for their ability to produce cytokines in co-culture for livestock feed, to improve the immune systems of production animals such as dairy cattle.

Interestingly, feeding cattle directly with lactobacilli containing probiotics has no significant effect on methane production [6] however as a natural modifier in alfalfa silage, combined with gallnut tannin, it improves silage quality and modulates ruminal microbiota mitigating methane production [7].

Figure 1. Showing Lactobacillus strains for antibacterial activity testing on MRS agar, on Singer Instruments PlusPlate. Photograph courtesy of Dr. Sandra Kittelmann, Wilmar International Limited.

Lactobacillus in food production

Post-harvest uses of Lactobacillus include spoilage prevention, improvement of storage stability and safety and enhancement of taste [8].

The antimicrobial properties of lactobacilli have many uses, such as in cheese spread to reduce listeria monocytogenes [9]. When tested in vivo the antimicrobial properties of lactobacilli produce zones of inhibition on agar plates.

Figure 2. A colony picker, such as Singer Instruments’
PIXL can identify and measure zones – efficient for screening strains
with the strongest antimicrobial properties.

Foods that contain lactobacilli, such as milk and yogurt, provide a huge health benefit to us. Lactobacilli in probiotics for humans can influence the immune response by modulating inflammatory mediators, and this can be used to make precision probiotics for therapeutic uses.

Lactobacillus increases CD40 and CD80 expression to inhibit tumour growth and increase caspase 1 to increase cleavage of IL-1B and IL-18 into their active form to stimulate the innate immune system. Lactobacillus can also increase Treg cell number for the prevention of autoimmune diseases [10].