Production of fungal laccase on pineapple waste and application in detoxification of malachite green.

The main purpose of this work was to use pineapple crowns as substrate for optimizing laccase production by in lab-scale experiments. One-factor-at-the-time analysis and response surface methodology were used to optimize production. A single laccase with molecular weight of 45 kDa was the main protein produced. A maximal laccase activity of 60.73 ± 1.01 U/g was obtained in 7-day cultures, representing a 6.7-fold increase compared to non-optimized conditions. The optimized conditions were temperature: 28 °C; initial moisture: 90%; glucose: 8.38%; yeast extract: 2.86%. Combining activity and stability, the best conditions for using this laccase during the long periods required by large-scale processes are pH 4.0-5.0 and temperature of 40-50 °C. Under these conditions, the crude laccase was efficient in detoxifying the dye malachite green with a K of 14.33 ± 1.94 µM and a V of 0.482 ± 0.029 µM/min with 0.1 units/mL. It can be concluded that pineapple crown leaves can be effectively used as substrate by for producing laccase under solid-state culture conditions. Laccase is an industrially relevant enzyme and its production with concomitant valorization of pineapple crowns as substrate offers highly interesting perspectives.