Production, purification and characterization of laccase from Pleurotus ostreatus grown on tomato pomace

Yellow laccase produced by Trametes versicolor K1 on tomato waste: A comparative study with the blue one produced on semi-synthetic medium

Laccase production by fungal growth on agrifood waste is still poorly studied. Trametes versicolor K1 isolated from palm bark produced a yellow non glycosylated laccase from tomato waste based medium (TMT) and a blue glycosylated laccase on glucose medium (GLU). Lignocellulosic biomass, such as pinecones (PIN), palm leaves (PLM), olive pomace (OLV), and alfa stems (ALF) have also been used as growth medium for T. versicolor K1. In these conditions, very low or no laccase production was observed. When peptone was supplied in TMT medium, the laccase activity increased from 4170 U/L to 8618 U/L. By increasing the culture volume up to 1 L, laccase production on TMT was 9929 U/L. The yellow laccase (TmtLac) was purified from the supernatant TMT medium and has shown similar characteristics with the blue laccase (GluLac) purified from the GLU medium. Their apparent protein size was 63 kDa. Catalytic activities of the yellow form were not very different from those of the blue form, but specific activity of the purified yellow laccase produced on tomato waste was much higher. The K_m and V_m values for four substrates, ABTS, DMP, guaiacol, and pyrogallol were almost similar for both isoenzymes. The optimum pH and temperature were respectively 4.0 and 50 °C. Although the level of glycosylation is clearly different, the thermostability of TmtLac and GluLac are quite similar. TmtLac is even slightly more tolerant at 60 °C for 24 h than GluLac. Moreover TmtLac showed greater stability at alkaline pH after 24 h compared to that of GluLac.We demonstrate that activity of the yellow TmtLac is not significantly affected compared to the blue laccase and that tomato waste is a simple and interesting lignocellulosic substrate to the laccase producer Trametes sp.

Purification and biochemical characterization of a new thermostable laccase from Enterococcus faecium A2 by a three-phase partitioning method and investigation of its decolorization potential

Three-phase partitioning (TPP) is a simple, fast, cost-effective, and highly efficient process that can be used in the purification of laccases. In this study, microorganisms with laccase activity were isolated from water samples collected from the Agri-Diyadin hot spring. The isolate with the highest laccase activity was found to be the A2 strain. As a result of molecular (16S rRNA sequence) and conventional (morphological, biochemical, and physiological) analyses, it was determined that the A2 isolate was 99% similar to Enterococcus faecium (Genbank number: MH424896). The laccase was purified to 4.9-fold with 110% recovery using the TPP. The molecular mass of the enzyme was found by SDS-PAGE to be 50.11 kDa. Optimum pH 6.0 and optimum temperature for laccase were determined as 80 °C. The laccase exhibited pH stability over a wide range (pH 3.0-9.0) and a high thermostability, retaining over 90% of its activity after 1 h of incubation at 20-90 °C. The laccase exhibited high thermostability, with a heat inactivation half-life of approximately 24 h at 80 °C. The enzyme remained highly stable in the presence of surfactants and increased its activity in the presence of organic solvents, Cr²⁺, Cu²⁺, and Ag⁺ metal ions. The K_m, V_max, k_cat, and k_cat/K_m values of laccase for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) substrate were 0.68 mM, 5.29 μmol mL^-1 min^-1, 110.2 s^-1, and 162.1 s^-1 mM^-1, respectively.

Degradation of sulfonamides in aquaculture wastewater by laccase-syringaldehyde mediator system: Response surface optimization, degradation kinetics, and degradation pathway

As a new type of environmental pollutant, environmental antibiotic residues have attracted widespread attention, and the degradation and removal of antibiotics has become an engaging topic for scholars. In this paper, Novozym 51003 industrialized laccase and syringaldehyde were combined to degrade sulfonamides in aquaculture wastewater. Design Expert10 software was used for multiple regression analysis, and a response surface regression model was established to obtain the optimal degradation parameters. In the actual application, the degradation system could maintain a stable performance within 9 h, and timely supplement of the mediator could achieve a better continuous degradation effect. Low concentrations of heavy metals and organic matter would not significantly affect the degradation performance of the laccase-mediator system, making the degradation system suitable for a wide range of water quality. Enzymatic reaction kinetics demonstrated a strong affinity of sulfadiazine to the substrate. Ten degradation products were speculated using high-resolution mass spectrum based on the mass/charge ratios and the publication results. Four types of possible degradation pathways of sulfadiazine were deduced. This work provides a practical method for the degradation and removal of sulfonamide antibiotics in actual sewage.

Evolving stability and pH-dependent activity of the high redox potential Botrytis aclada laccase for enzymatic fuel cells

Fungal high redox potential laccases are proposed as cathodic biocatalysts in implantable enzymatic fuel cells to generate high cell voltages. Their application is limited mainly through their acidic pH optimum and chloride inhibition. This work investigates evolutionary and engineering strategies to increase the pH optimum of a chloride-tolerant, high redox potential laccase from the ascomycete Botrytis aclada. The laccase was subjected to two rounds of directed evolution and the clones screened for increased stability and activity at pH 6.5. Beneficial mutation sites were investigated by semi-rational and combinatorial mutagenesis. Fourteen variants were characterised in detail to evaluate changes of the kinetic constants. Mutations increasing thermostability were distributed over the entire structure. Among them, T383I showed a 2.6-fold increased half-life by preventing the loss of the T2 copper through unfolding of a loop. Mutations affecting the pH-dependence cluster around the T1 copper and categorise in three types of altered pH profiles: pH-type I changes the monotonic decreasing pH profile into a bell-shaped profile, pH-type II describes increased specific activity below pH 6.5, and pH-type III increased specific activity above pH 6.5. Specific activities of the best variants were up to 5-fold higher (13 U mg⁻¹) than BaL WT at pH 7.5.