Screening methods for the proteolytic breakdown of gluten by lactic acid bacteria and enzyme preparations

Gluten is the major protein in wheat and it is largely responsible for the rheological characteristics of bread dough. The sourdough process is a trad itional dough fermentation process with lactic acid bacteria. The proteolyt ic activity of lactic acid bacteria derived from starter cultures used in s ourdough or meat fermentation was tested on gluten as a substrate. The acti vities of commercial enzyme preparations, which were derived from bacterial or fungal sources, were also evaluated. Proteolytic breakdown of gluten pr otein in an agar medium by either bacterial culture or enzymes was evident by a clear zone around wells after staining with Coomassie blue. The increa se in TCA-soluble material due to gluten breakdown was measured spectrophot ometrically. A third test evaluated the release of free amino acids due to exoproteolytic activity. The agar based test showed positive results for th e commercial enzyme preparations and one Micrococcus strain. All sourdough strains were positive in the enzyme test whereas some starters from the mea t fermentation process were not able to break down gluten under test condit ions. Variations in the release of free amino acid indicated differences in the enzyme systems of the lactic acid bacteria tested.