A water activity control system for enzymatic reactions in organic media

✍ Scribed by Anna E.V. Petersson; Patrick Adlercreutz; Bo Mattiasson

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 164 KB
• Volume: 97
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.21229

✦ Synopsis

Abstract

A water activity control system for enzymatic synthesis in organic media, for litre‐scale reactors has been constructed. Water activity, a~w~, is a key factor when using enzymes in non‐conventional media and the optimum value varies for different enzymes. The control system consists of a water activity sensor in the headspace of a jacketed glass reactor (equipped with narrow steel tubes to introduce air), gas‐washing bottles containing blue silica gel (a~w~ = 0) and water (a~w~ = 1), a PC to monitor water activity and a programmable logic controller (PLC) to control the water activity. The system was evaluated by adjusting water activity in the medium, with a deviation from the set point of less than ±0.05. Synthesis of cetyl palmitate, under controlled water activity and catalysed by two different lipase preparations, namely, Novozym® 435 (immobilised Candida antarctica lipase B) and immobilised Candida rugosa lipase, were also performed. Novozym® 435 catalyses reactions very well at extremely low water activity while C. rugosa lipase shows low activity for a~w~ < 0.5. Biotechnol. Bioeng. 2007;97: 235–241. © 2006 Wiley Periodicals, Inc.