Proteolysis during tempe fermentation

Abstract

The proteolytic capacity of 36 strains of the genus Rhizopus isolated from Indonesian tempe or tempe inocula was examined. No significant changes in the total amount or pattern of amino acids could be found, but there was a distinct increase in the amount of free amino acids. Strains with a high proteolytic activity were found, which were able to release nearly five times more amino acids after standard fermentation than others. Changes in fermentation parameters such as temperature or relative humidity improved these results. Fermentations with mixed populations of bacteria and Rhizopus yielded a lower level of free amino acids, but an increased total amount of amino acids. Examination of protease systems of three Rhizopus species showed that the proteases of the cell wall fraction were most responsible for proteolytic capacity of the different strains. On average their activity amounted to 71% of the total proteolytic capacity.