Amylase production by Aspergillus oryzae in a solid‐state bioreactor with fed‐batch operation using mussel processing wastewaters as feeding medium

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.