Enzymatic hydrolysis assisted with ligninocellulolytic enzymes from Trametes hirsuta produced by pineapple leaf waste bioconversion in solid-state fermentation

Solid-state fermentation (SSF) is an efficient technology to produce compounds of economic interest that allow the reduction of production costs when lignocellulosic residues, such as pineapple leaf waste (PLW), are used both as a carbon source and as support for productive microorganisms. In this work, three strains of Trametes hirsuta were evaluated for PLW bioconversion into fermentable sugars and the production of laccases by SSF technology. SSF experiments were performed at 27 and 35 °C for 21 days. The highest level of laccase activity was obtained at 27 °C in SSF with T. hirsuta AHB-6 (6513.8 U/mL). However, the greater PLW delignification rate (28%) was observed in biomass SSF with T. hirsuta RT-1 at 35 °C. Structural changes allowed sugar yields until 90.8% from cellulose. Enzymatic hydrolysis achieved a reducing sugar concentration of 580 mg/g PLW biomass, while in assisted enzymatic hydrolysis (with an enzymatic crude extract from SSFs), up to 2.5 times higher reducing sugar concentration than control. The characterization of the recovered fermentable sugars showed that hemicellulolytic enzymes are present in the crude enzymatic extracts of T. hirsuta and that in synergism with commercial cellulases allowed the 100% saccharification of the holocellulose. Since PLW showed suitable characteristics as a substrate for T. hirsuta, the addition of another nutrient was not necessary to obtain functional lignocellulolytic enzymes, as well as possible antioxidants and proteins. These results can lead to a low-cost and efficient process under the biorefinery concept.