The present report reviews the potential and applicability of industrial microbe side streams produced in Finnish bioprocess industries for biosorption of heavy metals from wastewaters. Microbial side stream biomasses are formed worldwide in e.g. food, brewing, biofuel, pharmaceuticals, wood processing and enzyme manufacturing industries. Although these streams are typically used for low-valued animal feed or biogas production, they would also have potential for biosorbent materials to be used in in situ water treatment. Since major challenges have been recognized, especially regarding the availability of biomass, and to logistic and processing cost, biosorption is not the most economically attractive option for the use of these biomasses at the moment. However, in the future the situation may change due to new incentives or more cost-efficient biosorbent preparation technologies. This report will provide a knowledge basis for the consideration of biosorption applications for industrial microbe side streams. Journal of Bior emediation & Biodegradation Yeast fermentationsEthanol fermentation process consists of several unit operations to convert carbohydrates into ethanol by S. cerevisiae. This technology is employed worldwide in production of alcoholic beverages and bioethanol. After brewing the yeast cells are collected from the bottom of tank or separated by centrifugation to form slurry of 20-50% solids [6]. Loose slurries are further concentrated by filtration after which they are thermally disrupted at around 80°C and optionally also with organic acids. The production capacity of major Finnish breweries is over 400 million l/a [7] and the respective quantity of formed yeast containing residues is approximately 2000 t/a.Bioethanol is produced by St1 Biofuels Oy in quantity of 13,000 t/a in Lahti, Vantaa, Hamina, Jokioinen and Hämeenlinna. Ethanol is further concentrated at Hamina. These production sites produce altogether over 75,000 t/a of residues that contain also yeast cells. Hämeenlinna plant directs all organic residues to biogas production [8] while the other plants produce also animal feed. The amount of produced feed is over 45,000 t/a [9][10][11][12]. The company has also been appointed an environmental permit in 2013 for production of lignocellulose ethanol in Kajaani [13]. Yeast residues of the process together with other residues would be directed to energy production. Enzyme productionThe main steps in enzyme production processes are medium preparation, inoculum preparation, inoculation and fermentation, cell removal, product purification and concentration, and formulation. The nature of produced enzyme affects also properties of microbial residues. Extracellular enzymes are recovered from the fermentation broth after removal of cells which remains the cells intact. Cell removal is conducted using filter press together with filter aids and flocculants. On the contrary, intracellular products are recovered via disruption of cells by chemical or mechanical methods, after which cell debri...