Influence of Oxygen Supply on Growth and Laccases Production by Pleurotus sajor-caju PS-2001 in Submerged Process

Abstract

(1) Background: Oxygen supply is an important parameter to be considered in submerged cultures. This study evaluated the influence of different conditions for dissolved oxygen (DO) concentration on laccases activities and growth of Pleurotus sajor-caju PS-2001 in submerged process in stirred-tank bioreactor. (2) Methods: Initially, three different conditions were tested: uncontrolled DO and minimum levels of 30% and 80% of saturation, with the pH controlled between 4.5 and 7.0. (3) Results: Best results were observed at 30% DO (26 U mL-1 of laccases at 96 h), whereas higher mycelial biomass was observed at 30% and 80% DO (above 4.5 g L-1). Four different conditions of DO (uncontrolled, 10%, 30% and 50% of saturation) were tested at pH 6.5, with higher laccases activity (80 U mL-1 at 66 h) and lower mycelial growth (1.36 g L-1 at 90 h) being achieved with DO of 30%. In this test, the highest values for volumetric productivity and specific yield factor were determined. Under the different pH conditions tested, the production of laccases is favoured at DO concentration of 30% of saturation, while superior DO levels favours fungal growth. (4) Conclusion: The results indicate that dissolved oxygen concentration is a critical factor for the culture of P. sajor-caju PS-2001 and has important effects not only on laccases production but also on fungal growth.

Laccases as green and versatile biocatalysts: from lab to enzyme market—an overview

“…c. Plant laccases Plant laccases were first reported in purified sap of the lacquer tree (known as urushi) from the Rhus vernicifera tree (Alcalde 2007). In plants, this enzyme plays important regulatory roles, such as the polymerization of lignin, the response to environmental stress, defense mechanism, wound healing, maintenance of the structure and the polymerization of phenolic compounds (Sharma and Kuhad 2008;Berthet et al 2012;Wang et al 2015a;Janusz et al 2020). In addition, Bryan et al (2016) Both plant and fungal laccases are glycosylated enzymes, and the carbohydrate fraction is mainly composed of mannose, N-acetyl glucosamine and galactose.…”

“…Some important parameters to be evaluated for the cultivation of fungi in a bioreactor include morphological growth (formation of pellets in submerged/agitated cultures and mycelia in solid-state cultures), agitation, mass transfer, oxygenation, broth rheology, pH, temperature, mode of operation (batch or continuous) and the cost of culture media. Airlift or Stirred Tank (STR) bioreactors with low mechanical agitation, provide a low shear environment to produce fungal laccases, preventing friction and damage in mycelial morphology and allowing the pelletized growth of fungi and a satisfactory enzymatic production (Wang et al 2016 ; Bettin et al 2020 ). Production of laccases in bioreactors (except Erlenmeyer flasks) using solid-state fermentation (SSF) is much less reported in the scientific literature than submerged cultivation (Wang et al 2019 ).…”

“…Airlift or Stirred Tank (STR) bioreactors with low mechanical agitation, provide a low shear environment to produce fungal laccases, preventing friction and damage in mycelial morphology and allowing the pelletized growth of fungi and a satisfactory enzymatic production (Wang et al 2016 ; Bettin et al 2020 ).…”