The performance of a novel, hydraulically operated cell disrupter has been investigated. The micro-organism used was bakers’ yeast (Saccharomyces cerevisiae) and glucose-6-phosphate dehydrogenase (G6PDH) was used as a marker enzyme. The yeast could be disrupted by a single pass through the apparatus and the enzyme release was a function of the operating pressure. The equipment is considered to be superior to conventional homogeniser pumps due to the limited temperature rise observed between the feed and the lysate for comparable levels of protein release.