Biomass (Dec 2023)

Laccase and Biomass Production via Submerged Cultivation of <i>Pleurotus ostreatus</i> Using Wine Lees

  • Georgios Bakratsas,
  • Kyriakos Antoniadis,
  • Panagiotis E. Athanasiou,
  • Petros Katapodis,
  • Haralambos Stamatis

DOI
https://doi.org/10.3390/biomass4010001
Journal volume & issue
Vol. 4, no. 1
pp. 1 – 22

Abstract

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Large quantities of wine lees are produced annually by the wine industry. The high phenolic content makes them unsuitable for disposal in the environment or animal feed without a suitable treatment. In this study, wine lees were treated by Pleurotus ostreatus in submerged cultivation, producing a high-value biomass and elevated levels of laccase, an important industrial enzyme. Biomass and laccase production reached 21 g/L and 74,000 Units/L, respectively, at the optimal conditions of initial pH 6.0, 20% v/v wine lees, 30 g/L glucose, and 20 g/L yeast extract, while decolorization and dephenolization rates of the waste were over 90%. The mycelial biomass was rich in proteins and essential amino acids reaching up to 43% and 16% per dry weight, respectively. Carbohydrates and lipids were the second richest bioactive compound in biomass, with values of 29.4 ± 2.7% and 29.5 ± 2.7%, respectively. The crude laccase in the culture supernatant was purified via a simple two-step purification procedure by 4.4-fold with a recovery of 44%. The molecular weight of the enzyme was determined to be 62 kDa via SDS electrophoresis. Enzyme activity was optimal at pH 5.0 and 70 °C. The activation energy of the enzyme was calculated at a value of 20.0 ± 0.2 kJ/mol. The pH stability and thermostability of the purified laccase were studied. The enzyme was remarkably stable at pH 8.0 and at temperatures up to 40 °C. The thermal inactivation energy of the enzyme was determined to be 76.0 ± 1.2 kJ/mol. The thermodynamic parameters (ΔH*, ΔG*, and ΔS*) for the thermal deactivation of the purified laccase at a temperature range of 20–60 °C were: 73.8 ≤ ΔH* ≤ 74.3 kJ·mol−1, 98.7 ≤ ΔG* ≤ 101.9 kJ·mol−1, and −90.5 ≤ ΔS* ≤ −84.3 J·mol−1·K−1. Wine lees could be ideal substrates of fungal cultivation for laccase production and biomass with a high protein content in an eco-friendlier way.

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