An expression system matures: A highly efficient and cost-effective process for phytase production by recombinant strains of Hansenula polymorpha

An efficient process was developed for the low-cost production of phytases using Hansenula polymorpha. Glucose or glucose syrups, previously reported as repressive substrates, were used as main carbon sources during fermentat ion. Glucose was even the most productive substrate for high-level producti on of phytases. Compared with the process using glycerol, the standard carb on source used for this process until now, the use of glucose led to a redu ction of more than 80% in the raw materials costs. In addition, exceptional ly high concentrations of active enzyme (up to 13.5 g/L) were obtained in t he medium, with phytase representing over 97% of the total accumulated prot ein. These levels greatly exceed those reported so far for any yeast-based expression system. Very efficient downstream processing procedures were dev eloped with product recovery yields over 90%. Both the fermentation and dow nstream processing were successfully tested in pilot scale up to 2000 L. As a result, H. polymorpha can be used as a highly competitive system for low -cost phytase production. (C) 1999 John Wiley & Sons, Inc. Biotechnol Bioen g 63: 373-381, 1999.