Experimental design and solid state fermentation: A holistic approach to improve cultural medium for the production of fungal secondary metabolites

Quentin Carboué,Magalie Claeys-Bruno,Isabelle Bombarda,Michelle Sergent,Jérôme Jolain,Sevastianos Roussos

doi:10.1016/j.chemolab.2018.03.011

Abstract

Solid-state fermentation (SSF) is a cultural method that holds tremendous potentials for the production of numerous microbial value-added compounds in various industries. As for every other process, experimental designs can provide tools to improve the product yields, diminish the production time and thus eventually decreasing the cost of the whole process. However, SSF, because of its solid nature, implies some constraints which consequently require specific tools to efficiently overcome them. The aim of this study was the improvement of the production of antioxidant naphtho-gamma-pyrones produced by Aspergillus niger G131 cultivated using SSF. Two experimental designs were presented, a combined design, taking into account two different types of variables to determine a proper solid medium, and a screening design with mixed-level factors to find solutes with significant positive effects on the output.

Highlights

Solid-state fermentation (SSF) is defined as the fermentation involving solids in absence of free water; substrate must possess enough moisture to support growth and metabolism of microorganisms [1]
Most studies investigate with precision the effects of chemical complementation with soluble compounds and physical parameters such as temperature and humidity but neglecting the definition of a proper solid medium [2,7,8,9,10,11,12]
In this study we investigated the medium optimization using a holistic strategy, to improve the production of naphtho-gamma-pyrones (NγPs) – secondary metabolites showing interesting antioxidant properties – by Aspergillus niger G131 cultivated on solid support

Summary

Introduction

Solid-state fermentation (SSF) is defined as the fermentation involving solids in absence (or near absence) of free water; substrate must possess enough moisture to support growth and metabolism of microorganisms [1]. The SSF system offers several economical and practical advantages including high product concentration, improvement of product recovery, simple cultivation equipment, lower plant operational, potential direct utilization of the crude fermented products and the possibility to use agro-industrial byproducts instead of synthetic ingredients as substrate, thereby to cost cutting the bulk of the production [2,3] These solid byproducts could be either a source of carbon and other nutrients or an inert support material for absorption of nutrients and biomass anchorage. Most SSF bioprocess optimization studies use response surface methodology (RSM), which is a powerful statistical and mathematical method for testing multiple process variables and their interactions simultaneously with limited experimental trials compared to “one-factor-at-a-time” approach [6] These optimizations are always achieved on a defined solid medium, selected using a classical one-factor-at-a-time approach. The solid medium composition was defined using combined designs – with mixture and discrete variables – and the

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Conclusion