Method of purifying a protein from fermentation solids under desorbing conditions

A method of purifying a protein of interest from particulate matter of a fermentation broth comprising the steps of

• A) separating the particulate matter from the fermentation broth resulting in a solid portion of the fermentation broth comprising the particulate matter and a liquid portion of the fermentation broth,
• A2) providing a washing solution comprising one or more conditions that favor solubilization of the protein of interest and/or the desorption of the protein of interest from the particulate matter, wherein one of the conditions comprises:
• a) a pH value above the pI value of the protein of interest;
• or
• b) a pH value below the pI value of the protein of interest and under these conditions a positively charged compound in a concentration leading to a conductivity of 1-100 mS/cm of the washing solution, and
• B) conducting one or more washing steps comprising contacting the solid portion of the fermentation broth comprising the particulate matter with a volume of the washing solution to form a resulting solution and removing the same or similar volume of liquid from the resulting solution, whereby the protein of interest is solubilized and/or released from the particulate matter into the resulting solution.