A mannanase at least 85% identical to SEQ ID NO: 1, a polynucleotide encoding the mannanase, an expression construct comprising the polynucleotide, and a host cell comprising the polynucleotide or the expression construct.

The present invention relates to the field of industrial fermentation and protein production. In particular, it relates to a method for producing a protein of interest in a fermentation medium comprising the following steps a) inoculating a fermentation medium with a Bacillus host cell comprising a gene encoding a protein of interest under the control of a promoter; b) cultivating the Bacillus host cell in the fermentation medium under conditions conducive for the growth of the Bacillus host cell and the expression of the protein of interest, c) adding sulfate to the fermentation medium to reach a concentration of at least 20 mM of sulfate in the fermentation medium; and d) allowing the protein of interest to precipitate and/or crystallize during cultivation; wherein the fermentation medium comprises an amino acid derivative in an amount of 0-30 g/l of fermentation medium. Further contemplated is the use of a combination of a sulfate and an amino acid derivative for producing a protein of interest in Bacillus host cell in a fermentation medium and a crystallized protein of interest obtained by or obtainable by the method of the invention.

A mannanase at least 75% identical to SEQ ID NO: 2 or SEQ ID NO: 3, a polynucleotide encoding the mannanase, an expression construct comprising the polynucleotide, and a host cell comprising the polynucleotide or the expression construct.