[BojanaL]

What I like the most about bioremediation is that microorganisms used for “cleaning” could serve multiple purposes after they finish their primary industrial role.

Spirulina (Arthrospira platensis) is green microalgae cultivated worldwide and used as a food supplement, to enhance detoxification of the organism, to improve digestive health, to increase muscle mass in athletes, to support cardiovascular function and improve cholesterol level, to strength the immune system, to reduce allergy in children, to decrease cancer risks and to provide general health. It could be used in a form of tablets, powder or flake.

It’s very popular food supplements as it contains all necessary nutrients. 60% of algea’s dry weight is protein (containing all essential amino acids), plus it’s rich in carbohydrates, vitamins, pigments, antioxidants…. Lipids content is not very high (7%) but all important lipids like: gamma-linolenic acid, alpha-linolenic acid, linoleic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid are present. List of vitamins in Spirulina is long: B1, B2, B3, B6, B9, vitamin C, vitamin D, vitamin A and vitamin E. All vital microelements such as K, Ca, Cr, Cu, Fe, Mg, Mn, P, Se, Na and Zn, could be obtained from Spirulina as well. Pigments are acting as antioxidants, providing protection against various infections and diseases and slowing down aging process. Most important antioxidants for human health that could be found in Spirulina are: beta-carotene, zeaxanthin, chlorophyll-a, diatoxanthin, beta-cryptoxanthin, xanthophyll, canthaxanthin…

Studies in human and animals showed that Spirulina is safe and doesn’t have any adverse effect when replacing conventional proteins in diet. Those were experiments having Spirulina grown in the clear water; effluent water as a cultivating medium has never been used before.

Due to increased need for fish proteins in the world, fish farming became very popular method of raising fish in tanks and enclosures that will eventually be sold as a food. In 2008, 33.8 million tones of fish worth ~60 billion dollars were produced in the world. Maintaining of the tanks (temperature, pH, acidity, micronutrients…) and providing enough food for the fish are what make pisciculture (fish farming) very expensive business. A lot of different fish species are raised this way, most commonly tilapia, cod, salmon, carp and catfish. Some of those species are carnivorous and some are depending on the plankton and water plants. In either way, proper nutritious is essential as fish biomass and quality of meat is directly associated with the provided meals. Tilapia is very old herbivorous fish species raised often for food as it grows fast and could tolerate poor water quality. Spirulina could be a good food source for the fish and experiment with algae grown on the effluent water was undertaken to check if this is could be safe and nutritionally satisfying source of food for the tilapia.

Gelatin is used in pharmaceutical (medicine capsules), food (jellied desserts), and paper and photo industry (photographic plate coatings). It’s made by boiling animal derived connective tissue (bones, tendons…). Effluent from the gelatin manufacturing industry needs to pass couple of treatments before used as a cultivation media for Spirulina. Close attention was paid on the growth, metabolism and reproduction of the fish. First group of fish was fed on regular diet (control group), second group had 30% of regular diet replaced with waste water harvested Spirulina and third group was fed up on 50% of Spirulina meals. Experiment lasted for 120 days and results were better than expected.

Survival rate in all group were the same. Growth rate was higher in Spirulina fed groups; fish were longer, wider and heavier in two group eating Spirulina meals. Reproductive behavior, metabolic functions, excretion and movements were unchanged compared to control group.

This experiment provides valuable information for two reasons. First it’s shown that Spirulina grown in the waste water could be a perfect substitute for the expensive conventional fish food. Second it showed that classic fish meal could be replaced by 50% with Spirulina without causing any adverse effects. This is very important finding considering that fish farming is large industry that is looking for any solution that could help decrease expenses, but at the same time could solve the problem of waste water in the industry of various kinds.