Does a powder of kombucha culture need a hechsher (its just a probiotic)?
ב"ה Shalom, I have not supervised kombucha production so I cannot tell you for sure that all is kosher in producing the culture. Furthermore, I have been told by a food chemist, that the kombucha tea has been known to have adverse effects in certain circumstances. Therefore, I will simply adopt what the OU organization has recommended in its website and that is not to brew it on your own but to obtain it from certified kosher and FDA approved company. All the best