Cane and beet molasses processed via submerged methods gave citric acid (CA) synthesis approximates to 100 g dm^-3. Beet molasses can also be used for biochemical production of oxalic acid (OA) giving 38.7 g dm^-3 of product. However, molasses is not appropriate substrate for gluconic acid (GA) synthesis as only half of hydrolyzed saccharose can be converted by glucose oxidase to product. The same problems appear with reference to sugar cane bagasse and sugar beet pulp, but these solid wastes can successfully be applied for other organic acid biosynthesis by solid-state method. Enrichment them by carbon source allowed obtaining 132 and 204 g kg^-1 d.s. of CA, respectively. Hydrol bioconversion by submerged method gave high CA output approximates to 120 g dm^-3. Mixture of wastes remaining after separation of gluten and starch from wheat flour makes possible to obtain 30 g dm^-3 of citric acid. Finally, the solid wastes, i.e. wastes coming from a filtration stage in glucose syrups purification, processed by solid state fermentation, allowed obtaining 230 g of CA from approximately 1 kg of substrate used.

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