Ultrasound-intensified laccase production from Trametes versicolor

Abstract

a b s t r a c tAn efficient intermittent ultrasonic treatment strategy was developed to improve laccase production from Trametes versicolor mycelia cultures. The optimized strategy consisted of exposing 2-day-old mycelia cultures to 5-min ultrasonic treatments for two times with a 12-h interval at the fixed ultrasonic power and frequency (120 W, 40 kHz). After 5 days of culture, this strategy produced the highest extracellular laccase activity of 588.9 U/L among all treatments tested which was 1.8-fold greater than the control without ultrasound treatment. The ultrasonic treatment resulted in a higher pellet porosity that facilitated the mass transfer of nutrients and metabolites from the pellets to the surrounding liquid. Furthermore, the ultrasonic treatment induced the expression of the laccase gene (lcc), which correlated with a sharp increase in both extracellular and intracellular laccase activity. This is the first study to find positive effects of ultrasound on gene expression in fungal cells. These results provide a basis for understanding the stimulation of metabolite production and process intensification by ultrasonic treatment in filamentous fungal culture.

Chitosan multiple addition enhances laccase production from Trametes versicolor

“…El Ghaouth et al [10] reported the leakage of chitin deacetylase, amino acids and proteins through the chitosan-damaged cell wall of Rhizopus stolonifer. Increase in the porosity of the cell wall of T. versicolor and higher extracellular laccase activity in response to ultrasonic treatment have been reported [17].…”

“…Chitosan has been reported to induce higher synthesis of cell wall-associated enzymes, phenolic compounds, amino acids and some secondary metabolites in fungi [31,32]. Laccase secretion in filamentous fungi can be enhanced by lots of factors, which range from availability of saprophytic nutrients to morphological changes [17,33]. Chitosan could have facilitated increased synthesis of intracellular laccase and its efflux, thereby increasing the laccase activity in the medium.…”

“…Palma-gurrero et al, [29] reported the loss of cellular constituents and disorientation of the cytoplasm of Fusarium oxysporum exposed to chitosan treatment. Protracted exposure of T. versicolor cultured media to heat shock and ultrasonic treatment resulted in similar effects on laccase production [17,20].…”

“…Thus, there is a need to achieve cheap and robust production of this biocatalyst in microorganism hosts by means of chemical modification or protein engineering. Although laccase occurs in numerous microbes, it is produced mainly in the intra-and extracellular milieu of wood-degrading fungi [12,17]. One of the well-known families of fungi involved in laccase production are the white-rot fungi from basidiomycetes of which Trametes sp.…”

“…Strategic efforts geared toward achieving this include the use of inducers such as copper ion, tween 80 and phenolic-aromatic compounds [18,19]. Innovations such as heat shock treatment [20], recombination and heterologous expression of laccase gene [21] and ultrasonic treatment [17] have also been tested. Likewise, the use of corn steep liquor as an inducer and a nitrogen source for laccase production in T. versicolor was recently reported [22] Problems faced by some of these strategies include low yields of laccase, secretion of laccase isoenzymes and proteases, high cost of production, prolonged production time and inconsistent fungal growth [23].…”