Abstract
Fermentation in solid state culture (SSC) has been the focus of increasing interest because of its potential for industrial applications. In previous studies SSC of pomegranate wastes by Aspergillus niger has been extensively developed and optimized for the recovery of ellagic acid (EA), a high value bioactive. In this study we comparatively investigated the SSC of powdered pomegranate husks by A. niger and Saccharomyces cerevisiae and evaluated the recovery yields of EA by an ultrasound and microwave-assisted 7:3 water/ethanol extraction. Surprisingly enough, the yields obtained by S. cerevisiae fermentation (4% w/w) were found 5-fold higher than those of the A. niger fermented material, with a 10-fold increase with respect to the unfermented material. The EA origin was traced by HPLC analysis that showed a significant decrease in the levels of punicalagin isomers and granatin B and formation of punicalin following fermentation. Other extraction conditions that could warrant a complete solubilization of EA were evaluated. Using a 1:100 solid to solvent ratio and DMSO as the solvent, EA was obtained in 4% yields from S. cerevisiae fermented husks at a high purity degree. Hydrolytic treatment of S. cerevisiae fermented pomegranate husks afforded a material freed of the polysaccharides components that gave recovery yields of EA up to 12% w/w.
Highlights
The production of bioactives from agro-industrial by-products is nowadays a cutting-edge topic within circular economy systems and the use of biotechnological methods is one of the most actively pursued approaches
In the frame of a project aimed at exploitation of large amounts of wastes left after Saccharomyces cerevisiae fermentation of pomegranate fruits aided by addition of sucrose for production of wines, we found that extraction of these materials could afford ellagic acid (EA) in very good yields up to 4% (w/w with respect to the starting material) in an almost pure form [35]
In the present study this methodology was applied to S. cerevisiae yeast using pomegranate husk powder as support
Summary
The production of bioactives from agro-industrial by-products is nowadays a cutting-edge topic within circular economy systems and the use of biotechnological methods is one of the most actively pursued approaches. The advantage of this technique is the elevated volumetric productivity with high concentrations of products reached and much reduced effluent production. This technique has been applied to a variety of wastes produced in large amounts like rice bran, sugarcane bagasse, fruit pomaces, and peanut press cake to get mostly phenolic compounds by use of a variety of microorganisms [6,7,8,9,10]. These components are present in all parts of the fruit including peels, arils, and juice, and are responsible for a variety of biological activities that have been extensively documented [16,17,18]
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