Colour formation by bacterial nitric oxide synthase in fermented sausages inoculated with and without Mammaliicoccus vitulinus

In the present study, a Bacillus subtilis expression system was used to overexpress the gene of nitric oxide synthase (NOS), and the NOS was subsequently purified and added to fermented sausages to assess its colouration ability. The results indicated that NOS activity in the nos-recombinant strain was approximately 58-fold higher than that in the wild-type strain (P < 0.05). In a meat model system supplemented with metmyoglobin, the addition of NOS alone exhibited a significant effect on colour formation (P < 0.05), whereas inoculation with Mammaliicoccus vitulinus enhanced the red colour (P < 0.05). The results of the ultraviolet-visible (UV–vis) spectral analysis showed that more nitrosyl myoglobin (NO-Mb) was formed in the model system. In fermented sausages, the addition of NOS together with the inoculation of M. vitulinus led to a significant increase in the concentration of NO-Mb and the redness value (P < 0.05). The present study offers a potential solution for enhancing the colour formation in fermented sausages using an enzymatic method.