The Production of an Economical Culture Medium from Apple Pomace for the Propagation of Non-Conventional Cidermaking Yeast Starters

Abstract

The aim of the present study was to evaluate the use of different chemical treatments of apple pomace in order to produce an economical culture medium for the propagation of two non-conventional yeast strains. An experimental design approach was used for the optimization of the hydrolysis conditions of apple pomace. Both acid and alkaline treatment conditions were tested. The optimal hydrolysis conditions to disrupt the pomace lignocellulosic structure were 1% w/v of H3PO4, 121 °C, and 40 min for acid treatment, while 6% w/v of NH4OH, 20 °C, and 2 h were optimal for the alkaline condition. Saccharomyces uvarum NPCC 1420 and Saccharomyces eubayanus NPCC 1292 yeasts were able to grow in the liquid fraction obtained from both acid and alkaline treatments. However, the medium with the acid treatment was found to be more suitable for yeast growth, showing, for both strains, higher µmax and biomass production and lower td and λ than that observed for the medium with the alkaline treatment. According to the growth parameter analysis for both strains, the acid treatment was selected for further studies. By taking advantage of this agroindustrial by-product, a circular economy approach is promoted, reducing environmental impact and fostering sustainable development.

Keywords

• lignocellulosic wastes
• cider
• acid treatment
• alkaline treatment
• culture medium
• biomass propagation