Bacillus subtilis is a Gram-positive bacterium with great potential as a cellular factory for heterologous proteins. It has been used since the last century to produce enzymes and other active substances, it has a well-known genome and well developed tools for genetic genome modification. B. subtilis is very susceptible to accepting foreign DNA, accepting short PCR fragments in addition to chromosomal and plasmid DNA. It has an extremely flexible metabolism and can therefore grow on simple and inexpensive substrates. It excretes large amounts of product, mostly via the Sec and Tat secretion pathways, directly into the medium, making the purification process easier and cheaper. B. subtilis also has the advantage of GRAS status, it does not secrete endotoxins and exotoxins and does not produce inclusion bodies. In addition to the advantages, it also has some disadvantages. It is not able to form disulfide bonds as the enzymes are non-specific and slow. The biggest problem is the protease enzymes, which degrade the resulting heterologous proteins and reduce the yield of production. The best known products of B. subtilis are human growth factor and the industrial enzymes amylase, laccase, cellulolytic enzymes and xylanase.
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