Using bacterial metabolites to suppress the growth of pathogenic microbes on produce
Foodborne illnesses represent a significant threat to human health and safety, with many thousands of related deaths reported every year. At the same time there is a cultural drive towards adopting healthier diets and lifestyles. This usually involves incorporating more raw, unprocessed fruit and vegetables into the diet, which increases the risk of consuming contaminated food.
Of particular concern are tropical fruits. Tropical agricultural environments with warm temperature, high humidity and abundant availability of nutrients are the perfect breeding ground for potential pathogens. Contamination can originate from many different sources. Fields are fertilized with manure and irrigated with water which may contain pathogenic microbes. The fruits themselves have high sugar and water content and so are a perfect environment for microbial growth. After harvesting, there are many additional possible sources of contamination, including human handling, contact with equipment, contact with animals and washing with contaminated water.
Postharvest treatments are essential for preserving fruit by preventing spoilage and controlling the extent of microbial contamination. Some of these treatments involve the application of chemicals which in themselves present a risk to human health. There is therefore a drive to develop natural biological alternatives, known as biopreservation. This principle employs the use of probiotic microbes which are non-toxic and considered safe for human consumption, or even beneficial to human health. Probiotic microbes can be used for the preservation of fruit by utilizing their production of metabolites that suppress the growth of pathogenic microbes. In nature, these metabolites are produced by one species of microbe to suppress the growth of another species that is competing for the same resources. When these metabolites are derived from probiotic microbes, such as those from the genera Lactobacillus, Bifidobacterium, Weisella and Lactococcus, they are referred to as postbiotics and can be used as an agent of biological control for undesirable microbes on fruit.
Studies on the use of biopreservation and postbiotics have yielded promising results but have so far only been conducted in laboratory conditions and have yet to be scaled up and trialed fully. There is much that still needs to be fine-tuned about this approach such as what dosages are required and what application method is most effective. However, it does potentially offer an effective, safe and easily scalable alternative method for fruit preservation in the future.
The use of probiotics for reducing deterioration in tropical fruits is reviewed in the following article Postbiotics: a solution to protect tropical fruits towards postharvest adulteration