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Microbial catalysts having a combination of nitrile hydratase and amidase activities had a significantly-higher specific activity for hydrolysis of 3-hydroxyalkanenitriles than microbial nitrilase catalysts. Comamonas testosteroni 22 ± 1, Dietzia sp. ADL1 and Comamonas testosteroni 5-MGAM-4D nitrile hydratase/amidase biocatalysts each hydrolyzed 3-hydroxyvaleronitrile to 3-hydroxyvaleric acid (as the ammonium salt) in 99 ± 100% yields, but in consecutive batch reactions with catalyst recycle, alginate-immobilized C. testosteroni 5-MGAM-4D had superior enzyme stability and volumetric productivity. In a series of 85 consecutive batch reactions with biocatalyst recycle for the production of 1.0 M 3-hydroxyvaleric acid, the recovered nitrile hydratase and amidase activities in the final reaction were 29% and 40%, respectively, of the initial activities. The catalyst productivity for this series of reactions was 670 g 3-hydroxyvaleric acid/g dry cell weight (50 g 3-hydroxyvaleric acid/g biocatalyst bead), and the volumetric productivity of the initial reaction in the series was 44 g 3-HVA/L/h. Similar results were obtained with alginate-immobilized C. testosteroni 5-MGAM-4D for the hydrolysis of 3-hydroxybutryonitrile and 3-hydroxypropionitrile to the corresponding 3-hydroxyalkanoic acid ammonium salts.