Optimization of submerged fermentation conditions for gluten-degrading enzyme production using B. subtilis isolate

Abstract

In modern times wheat gluten has drawn attention to many research groups. Wheat gluten represents one of the most widely used proteins in the food industry. It is a byproduct of the starch industry and has a higher percentage of protein content compared to other plant-based protein sources. In order to help reduce the allergenicity of wheat gluten, bacterial enzymes have been proven to have beneficial results in wheat gluten treatment. In search for an extracellular peptidase producing strain we have tested Bacillus subtilis TMF-1 isolate, which has previously been proven to have several enzyme activities. B. subtilis TMF-1 isolate has a food grade status, making it safe for application in the food industry. Thus, the aim of this research was to examine the possibility of utilizing mentioned strain in terms of glutendegrading enzyme production. Tested strain was first streaked onto several agar plates in order to detect extracellular peptidase activity. Bacterial isolate has then been sequentially transferred to the same growth medium several times. Conditions varied for the submerged fermentation in 25 mL flasks were pH value of fermentation broth, concentration of gluten powder (0 - 10 g/L) in fermentation broth and concentration of peptone (0 - 1 g/L). Shaking flasks containing the fermentation broth with the bacterial strain were kept for 48 h at 37 0C. The results obtained show that the isolate has the possibility of thriving in low acidic to neutral pH values of the fermentation broth. Varied gluten concentrations showed that even 1 g/L of gluten powder was sufficient for the bacterial strain to manifest extracellular proteolytic enzyme activity. Peptone concentrations were also varied, but even the minimal presence of peptone has proven beneficial for bacterial growth and proteolytic activity. This research show that the B. subtilis TMF-1 isolate has proteolytic activity specific for wheat gluten as substrate and that it may be used in further research in order to utilize its enzymatic production abilities for lowering wheat gluten allergenicity.