Laccase production by Phomopsis liquidambari B3 cultured with food waste and wheat straw as the main nitrogen and carbon sources

Food waste is the most difficult waste to manage because of the high treatment costs and the risk of environmental contamination. Wheat straw burning has become an increasingly discussed topic in recent years because of the air pollution it causes. However, food waste and wheat straw contain high amounts of nutrient elements; efficient utilization of these wastes can improve the environment by lessening airborne pollutant emission and the amount of waste that must be landfilled. It is well known that use of low-cost and abundant waste materials in microbial fermentations can reduce product costs. We aimed to use these resources while improving laccase production by the endophytic fungus Phomopsis liquidambari B3. We cultured P. liquidambari B3 in medium containing food waste and wheat straw as the main nitrogen and carbon sources, respectively. We optimized the fermentation conditions by response surface methodology (RSM), using a Box–Behnken design for RSM I and a central composite design for RSM II. Optimization resulted in an 11.07-fold (1.98-fold RSM I; 5.59-fold RSM II) increase in laccase yield compared with that before optimization. The model was validated by mathematical evaluations and by comparisons between predicted and experimental values. Under optimized conditions, 53.76% of lignin in wheat straw was degraded. By optimizing fermentation conditions and using multiple bioresources, laccase production by this fungus was increased. These results provide the foundation for future research and for scaled-up laccase production.

Implications:

Food waste and wheat straw are waste products, but they could be bioresources if they were managed properly. In this work, we innovatively used a mixture of food waste and wheat straw as a substrate for the novel strain Phomopsis liquidambari B3 to produce laccase. This process, which provided the foundation for the subsequent research and for scaled-up laccase production, offers solutions for both rural and urban pollution problems: that is, it reduces the amount of waste material that needs to be disposed of by burning or dumping, and it also produces a valuable product.