Optimization of Bacillus cereus strain zk2 and Bacillus thuringiensis strain ILBB224 isolated from dairy sludge in reduction of histamine in vitro with ELISA by Response Surface Methodology

Biogenic amines are important compounds for physiological and metabolic functions in all living organisms that are produced by the metabolism of some amino acids and decarboxylation reactions during fermentation or food spoilage. Control of amine accumulation in fermentation products is one of the challenges in the food industry. Limiting microbial growth and decarboxylase activity of microorganisms by strains that lack of the enzyme amino acid decarboxylase or the oxidative strains of amines in starter cultures are their control methods. Therefore, in this study, the effect of Bacillus cereus strain zk2 and Bacillus thuringiensis strain ILBB224 isolated from dairy sludge alone and with cheese starter culture was investigated in both quantitative and qualitative reduction of histamine. A qualitative study was carried out through decarboxylation testing of bacterial strains in Lysine decarboxylase broth. The results indicated that strains lacked decarboxylation properties; thus, they were able to degrade histamine and reduce it, and by changing sugar and acid production, the color of the culture medium changed to yellow. Also, the effects of strains of Bacillus cereus strain zk2, Bacillus thuringiensis strain ILBB224 with starter culture of cheese on reduction of 50, 75, 100, 125 and 150 ppm of histamine were performed by ELISA. The results showed that with increasing histamine concentration, the reduction in histamine content was reduced by different strains. It was also found that the highest reduction in histamine was observed when using Bacillus strains with cheese starter at a concentration of 50 ppm histamine. Therefore, based on the findings of this study, these strains can be used as culture with the potential to reduce biogenic amines in different fermentation products.