University of Antwerp
Enhanced fungal delignification and enzymatic digestibility of poplar wood by combined CuSO4 and MnSO4 supplementation
Focus area / active in:
- Bioprocesses & technologies
- fungal pretreatment
- solid-state fermentation
- White-rot fungi
Biological pretreatment of lignocellulosic biomass by white-rot fungi is an environmentally friendly alternative to chemical and physical approaches to enhance enzymatic saccharification. However, inefficient lignin degradation and substantial cellulose consumption during fungal pretreatment can cause low sugar yields after enzymatic saccharification of the pretreated biomass. Since the ligninolytic ability of the fungal strains is highly dependent on the applied culture conditions, it is imperative to evaluate the application of suitable supplements to increase selectivity and effectivity of delignification by white-rot fungi.
In this research, the individual and combined effects of MnSO4 and CuSO4 supplements on the solid-state fungal pretreatment of poplar wood by Phanerochaete chrysosporium, a lignin and manganese peroxidase producing white-rot fungus, were investigated by using a Central Composite Design. The degree and selectivity of delignification were effectively improved by the combined application of MnSO4 and CuSO4 supplements. A 1.9 fold higher lignin degradation (26.9%) and a 2.3 times higher delignification selectivity value (2.4) were obtained in the pretreatment system supplemented with 2.01 μmol CuSO4 and 0.77 μmol MnSO4 g-1 DW wood. The improved delignification could be explained by increased and prolonged manganese peroxidase production that occurred due to the maintained stationary fungal growth phase.
The enhanced delignification greatly improved the enzymatic digestibility of poplar wood. Enzymatic saccharification of the combined supplemented pretreated wood resulted in 33.2% overall reducing sugar yield, which was 4.4 and 2.6 times higher compared to the untreated (7.5%) and non-supplemented pretreated wood, respectively. The highest reported increase in reducing sugar yield found in literature for a pretreatment system applying poplar wood and 4 weeks of pretreatment (conditions of present study) was only 2.0, but with a higher yield of 18.7% for the untreated wood and a final yield of 37% . The digestibility is strongly dependent on the applied starting material.
Figure 1: Reducing sugar yield in the function of MnSO4 and CuSO4 pretreatment variables
This study has demonstrated that the combined application of Mn2+ and Cu2+ can significantly improve the fungal pretreatment process and the beneficial effect of Cu2+ on delignification is not restricted to laccase producing white-rot fungi.
 W. Wang, T. Yuan, B. Cui, Y. Dai, Pretreatment of Populus tomentosa with Trametes velutina supplemented with inorganic salts enhances enzymatic hydrolysis for ethanol production, Biotechnol. Lett. 34 (2012) 2241–2246. https://doi.org/10.1007/s10529-012-1031-3.
Get in touch with the author!