Why does pasteurization not kill bacillus?

Pasteurization will kill the vegetative cells of Bacillus, what you are talking about are the spores of Bacillus species. The spores are very tough and can survive pasteurization, they require 121C for 30 minutes to be neutralized. read more

Not all types of bacteria are harmful. "Friendly" bacteria like Lactobacillus, Bifidobacterium and Saccharomyces cerevisiae take up residence in the human gut and crowd out the harmful bacteria. Beneficial bacteria are the same ones used to ferment and culture foods. read more

Pasteurization or pasteurisation is a process in which packaged and non-packaged foods (such as milk and fruit juice) are treated with mild heat (<100 °C) to eliminate pathogens and extend shelf-life. The process is intended to reduce spoilage organisms and eliminate vegetative bacteria but not bacterial spores. read more