Availability of Food for Man: The Role of Microorganisms

Before I studied Microbiology, anytime I heard microorganisms what always struck my mind was diseases and nothing more. I never thought anything useful comes from them. This also occur to so many other people, though. The study of microbiology has made us realize that microorganisms play both beneficial and harmful role in nature.

Microorganisms are living things that can not be seen with the naked eyes except with the aid of a microscope. They can be grouped into Bacteria, Fungi (Moulds and Yeasts) and viruses. Microorganisms are ubiquitous (i.e. they can be found everywhere). Microorganisms grow as man does (they are also living thing), the only difference is that microorganisms multiply themselves while man increase in size. They grow on a suitable medium which could be man's food. As they grow on food, they rather spoil the food or convert it to another useful/useless product.

Food, on the other hand, is any substance that can be consumed to provide nutritional support for man. Food can either be sourced from plants or animals. Be it as it may, food contains nutrients such as carbohydrate, protein, fats and oils, vitamins and minerals.

i. Mushrooms: Mushrooms are fungi (Agaricus spp), they are widely consumed in many countries off the world (Nigeria inclusive). Research have shown that mushrooms are rich in protein, fibre, vitamins B and D as well as minerals. However, as nutritious as mushrooms adequate selection of edible species is required because there are poisonous mushrooms (Amanita spp) which can kill man in few hours.

ii. Probiotics: Probiotics are food or dietary supplements which contain life microorganism. they are usually consumed by man for therapeutic reasons. A common example of probiotic is Yoghurt.

iii. Spirulina: Spirulina (Arthrosporus sp) is a photosynthetic and filamentous alga. It is widely consumed as food or as food supplement. it is rich in carbohydrate, protein, vitamin and minerals. Other algae that are consumed by man ar Chlorella spp and Dunaliella spp.

2. Microorganisms for food production

Over ages, man has explore microorganisms in the production of different food. The most well-known application of microorganisms in the food industry is fermentation. Fermentation is the conversion of carbohydrate (sugar) into acid and alcohol by microorganisms.

Fermentation is as old as history. In the olden days, man have taken advantage of natural fermentation in alcoholic beverages and dairy product. they didn't understood that microorganisms were responsible for the processes. Nowadays, with the advent of microbiology, fermentation is used to make an array of interesting foods and drinks. Fermentation gives food a good taste, texture and smell.

Below are some fermented food products widely consumed by man.

Harmful Roles of Microorganisms

1. Food spoilage

Despite playing a significant role in food production, microorganisms still have role to play in spoilage of available food. Food spoilage is the deterioration of food substances which makes them unfit or undesirable for human consumption. It affects the colour, odour, texture, consistency and nutritional value of foods. Food spoilage can be caused by microorganisms, chemical reactions, physical changes and vermin (weevils, ants, cockroaches etc).

Microbial spoilage occurs due to contamination and subsequent growth of microorganisms in foods and drinks. Foods may be contaminated by microorganisms during harvest, storage, processing, distribution, handling, or preparation. The primary sources of microbial contamination are soil, air, animal feed, and food processing machinery or utensils. Microorganisms could decompose (feed on) the nutritional content of foods and grow exponentially. By-products from the metabolic processes of the microorganisms are released in the food which makes it unacceptable by man.

Below are some microbial food spoilers and the food they spoil:
i. Lactic Acid Bacteria (LAB): Examples of LAB include Lactobacillus, Leuconostoc, Lactococcus, Streptococcus. They spoil beverages such as alcohol, fruit juices and dairy products.

ii. Acetic Acid Bacteria: Examples include Acetobacter, Gluconobacter, Acidomonas, Gluconacetobacter. They majorly spoil wines.

iii. Filamentous fungi (Moulds): Examples include Aspergillus, Penicillium, Fusarium, Alternaria. They spoil fruits, cereals, bakery products and some beverages.

iv. Yeasts: Examples include Saccharomyces, Candida, Blastoschizomyces. They spoil fruit and fruit-based products, alcoholic or carbonated beverages, salad dressings, dairy products and fermented foods.

v. Spore-forming Bacteria: Examples are Bacillus and Clostridium. They mostly spoil canned foods.

vi. Gram-negative Bacteria: Examples include Pseudomonas, Flavobacterium, Acinetobacter, Alcaligenes. They spoil meats, fishes and sea foods, egg, milk and dairy products.

2. Food poisoning

Another detrimental role of microorganisms in food is food poisoning. Food poisoning, also known as food-borne illness, is an illness that is caused by the consumption of food or drink contaminated by microorganisms, and/or their toxins, or with parasites or chemicals. Some cases of food poisoning may be mild (not severe) while some maybe life-threatening and can lead to death. Signs and symptoms of food poisoning are abdominal pain, diarrhoea, vomiting, nausea,fever, headache and loss of appetite.

Below are some organisms that cause food poisoning:
i. Campylobacter jejuni: It causes fever, abdominal pain and diarrhoea. It can be encountered in raw milk as well as under-cooked meat and poultry.

ii. Listeria monocytogenes: It causes fever, headache, septicaemia and meningitis. It can be encountered in soft cheeses, salad; cook-chill products.

iii. Escherichia coli: It causes diarrhoea and inflammations. It can be encountered in contaminated water, milk, inadequately cooked meat.

iv. Clostridium botulinum: It causes nausea, vomiting, double vision and paralysis. It can be encountered in faulty processed canned foods, cured meat and raw fish.

v. Salmonella spp: It causes diarrhoea and headache. It can be encountered in vegetables, poultry, eggs and raw egg products.

Conclusively, the roles of microorganisms in man's food cannot be underestimated. Generally speaking, man cannot survive on this earth without food. So man must carefully look at what brings food to their table (produces their foods) and what takes it away (spoils their food).