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Keywords:

  • amylase production;
  • mussel processing wastewaters;
  • solid-state;
  • salinization;
  • solid-state bioreactor;
  • fed-batch;
  • Weibull equation;
  • SSC;
  • SSF

Abstract

BACKGROUND: The high oxygen availability in solid-state cultures makes them especially suitable for fungal enzyme production. Glycogen-rich mussel processing wastewaters have been used successfully as substrates for amylase production by Aspegillus oryzae in solid-state cultures supported in polyurethane foam. The aim of this work was to study the fed-batch mode in a scalable solid-state bioreactor to extend the productive period and obtain high amylase production. Culture salinization due to the NaCl content of these wastewaters is the main drawback.

RESULTS: Evaporation of the excess liquid added during feeding led to progressive salt accumulation. The effect of culture salinization on amylase production was analysed and mathematically modelled, and the IC50 (65.4 g L−1 of NaCl) was calculated. An optimum operation mode for this bioreactor was designed that included foam extrusion for removing the incubated medium, washing and a final recharge with fresh medium every 72 h of incubation. This procedure kept the salt concentration under IC50 and increased the amylase production from 3000 to 12 000 UE g−1.

CONCLUSION: An operating mode with intermittent extrusions and washings of the support between feedings was found to be an appropriate procedure for preventing the accumulation of inhibitory compounds in fed-batch solid-state cultures. © 2012 Society of Chemical Industry