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The production of L-lactic acid from whey permeate, a waste product of the dairy industry, by fermentation with the lactic acid bacterium L a c t o b a c i l l u s casei subsp, casei was investigated. A fermentation medium consisting of permeate and supplements, which enables exponential growth of the organisms, was developed. A fast method for determination of free and immobilized biomass in solid-rich media, based on measurement of cellular ATP, was evolved. Continuous fermentations in a stirred tank reactor (STR) and in a fluidized bed reactor (FBR) with immobilized biomass were compared. In the STR a volumetric productivity of 5.5 g/1 per hour at 100% substrate conversion [dilution rate (D)---0.22 h -1] was determined. In the FBR porous sintered glass beads were used for immobilization and a maximum biomass concentration of 105 g/ kg support was measured. A productivity of 10 g/l per hour was obtained at D = 0.4 h-1 (substrate conversion 93%) and of 13.5 g/l per hour at D = 1.0 h -1 (substrate conversion 50%).

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Summary. Twenty two basidiomycetes, mostly white rot fungi, were grown on wheat straw. Lignin-, cellulose-, and hemicellulose-degradation was recorded in order to find a species growing on lignin preferably. The "oyster-mushroom" Pleurotus sp. "florida'" showed fastest delignification of all tested fungi.Straw pretreated by this fungus was fermented anaerobically to biogas. The gas yield produced from "myco-straw" is twice the amount from untreated straw.