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Vermiculite as a new carrier for extracellular protease production by Aspergillus spp. under solid-state fermentation

Summary

Researchers discovered that vermiculite, a naturally occurring mineral, is an excellent material for growing fungi that produce proteases—enzymes used in medicine, laundry detergents, and food processing. When Aspergillus fungi were grown on vermiculite using a technique called solid-state fermentation, they produced 3 to 18 times more protease than when grown on other materials. This discovery could make enzyme production more efficient and cost-effective for industrial applications.

Background

Solid-state fermentation (SSF) is a preferred technique for extracellular enzyme production by filamentous fungi, yielding 2-10 fold more hydrolases compared to submerged fermentation. Inert carriers such as polyurethane foam, perlite, and silica gel have been traditionally used for SSF. Vermiculite, a hydrated magnesium aluminum silicate mineral with high moisture capacity and porosity, presents a promising alternative carrier material.

Objective

To develop a new SSF system for protease production by Aspergillus species using vermiculite as a carrier and to compare its effectiveness with other inert carriers. The study aimed to evaluate protease productivity of Aspergillus ochraceus L-1 and Aspergillus ustus 1 on vermiculite versus polyurethane foam, perlite, and silica gel.

Results

Vermiculite demonstrated superior protease productivity with values of 52.4 and 57.2 U/mg of biomass for A. ochraceus L-1 and A. ustus 1 respectively, which was 3-18 times higher than other carriers tested. On day 6-8, maximum protease activities on vermiculite were 109.8 U/mg and 170.5 U/mg respectively, significantly exceeding results on silica gel. Both strains produced high levels of caseinolytic, fibrinolytic, and amidolytic proteases under SSF on vermiculite.

Conclusion

Vermiculite is a suitable and promising inert carrier for SSF of Aspergillus protease producers, providing 3-18 times higher mycelium productivity compared to other carriers and submerged fermentation. The superior performance of vermiculite is attributed to its physicochemical properties including porosity, moisture capacity, and ability to support fungal growth while maintaining enzyme activity, making it viable for industrial protease production.
  • Published in:Biotechnology Reports,
  • Study Type:Experimental Research,
  • Source: PMID: 33392004, DOI: 10.1016/j.btre.2020.e00576
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