TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The microorganisms comprise yeast, yeast like and/or bacteria. They also comprise yeast cells. They are from a wild type strain or genetically modified strain of yeast. Preferred Material: The conversion material comprises a biomass composed of treated biologically convertible matter and/or microorganisms detached from the supports.Preferred Method: The microorganisms allowed to fix, absorb, metabolize, alter, convert, digest or degrade the biologically convertible matter. They are also allowed to cause fermentation of the biologically convertible matter. The method comprises converting at least 0.1-90% biologically convertible matter into the conversion material. The elements in the biologically convertible matter are concentrated, fixed and recovered. A carbon source, nitrogen source, mineral, salt, amino acid or a product containing same is added to biologically convertible matter before contacting it with the microorganisms. The bioconvertible matter is treated in a continuous or a batch process. The microorganisms are immobilized onto the support under conditions promoting formation of glycoleme or thixotrope.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The carbohydrate source can be starch, amygladin, arbinose, cellobiose, esculin, fructose, galactose, glucose, lactose, maltose, mannitol, mannose, melezitose, melibiose, raffinose, rhamnose, ribose, salicin, sorbitol, sucrose, trehalose, xylose, cellulose and/or organic acids.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The bioreactor comprises air inlet disposed on the collection chamber and arrange to allow air to circulate biologically through the bioreactor. The distribution chamber comprises an exhaust arranged to allow exit of air ascending in the bioreactor.    TECHNOLOGY FOCUS - POLYMERS - Preferred Material: The supports are made of a polymer. EXAMPLE - Pig manure was injected at the top of a bioreactor. As pig manure which was rich in ammonia, the treatment of liquid containing yeast must be supplemented with a source of carbon, e.g., molasses and supplied with continuous oxygen. The bioreactor can be aerated at the bottom with polluted air from a pig sty that contained ammonia. The yeast or microorganisms to be immobilized on the supports was made to the capacity of the species to fix and to transform the substrate to be treated. The supports used in the bioreactor chamber were perforated polyester or vinyl membranes. They permitted fixation of yeast and exchanged of oxygen. The lattice was maintained vertically by a mechanical support. The result was the formation of a biomass from pig manure and a decreased of the odors resulting from a removal of ammonia by the yeast.