Fungal co-culture increases ligninolytic enzyme activities: statistical optimization using response surface methodology

The optimization of ligninolytic enzyme (LE) activities in a novel fungal co-culture between Pycnoporus sanguineus and Beauveria brongniartii were studied using a Plackett-Burman experimental design (PBED) and a central composite design (CCD). In addition, H₂O₂ role was analyzed. Laccase (EC. 1.10.3.2) and MnP (EC 1.11.1.14) activities of P. sanguineus increased 6.0- and 2.3-fold, respectively, in the co-culture with B. brongniartii. The H₂O₂ content was higher in the co-culture (0.33-7.12-fold) than in the P. sanguineus monoculture. The PBED revealed that yeast extract (YE), FeSO_4, and inoculum amount were significant factors for laccase and MnP activities and H₂O₂ production in the co-culture, which increased by 8.2-, 5.2- and 1.03-fold, respectively. The YE and FeSO₄ were studied using a CCD to optimize the studied response variables. Laccase activity was enhanced 1.5-fold by CCD, the optimal amount of YE was 0.366 g L^-1. Quadratic term of FeSO₄ modulated MnP activity and was associated with a 4.28-fold increase compared to the PBED. Both YE and its quadratic term significantly affected H₂O₂ production; however, the CCD did not enable an increase in H₂O₂ production. Pearson correlation indicated an increase in laccase (r²=0.4411, p = 0.0436) and MnP (r²=0.5186, p = 0.0198) activities following increases in H₂O₂ in the co-culture system.