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Keywords:

  • chitin;
  • chitinolytic enzymes;
  • submerged fermentation;
  • Serratia marcescens;
  • waste management

Abstract

The chitinolytic activity of submerged cultures of Serratia marcescens QMB1466 in media containing four forms of chitin as the main substrate was investigated via a full factorial design experiment with pH, temperature and substrate concentration as the main parameters. At the optimum conditions (pH 7.0, 32.5 °C and 1.0% (w/v) substrate), bioprocessed chitin (BP), isolated by lactic acid fermentation of prawn shell (Nephrops sp), induced a higher level of enzyme activity than untreated prawn shell and colloidal chitin but not that of a chemically isolated chitin (CP). The optimal conditions of pH and temperature were then applied in a bench-top bioreactor and the chitinolytic activity monitored temporally under the influence of higher concentrations of BP and CP. Increasing the concentration of substrate in the bioreactor (>1.0% w/v) was found to inhibit the enzyme activity of the bacteria. The enzyme mixtures in selected 120-h culture supernatants were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and the main proteins characterised by molecular weight. The electrophoretic patterns obtained from cultures from different experiments and by the different chitin substrates showed marked similarity and the main proteins isolated were largely homologous to well-documented chitinases found in the literature. BP chitin was found to be an efficient elicitor of chitinolytic activity from this bacterium and hence is a suitable substrate to employ in an integrated biotechnological process, whereby several commercially applicable products can be obtained from a waste product of the fishing industry. Copyright © 2004 Society of Chemical Industry