Tyrosinase, an enzyme involved in browning reactions in plants/crops exposed to mechanical injury, was isolated from the pulp of some different locally available bananas (M. cavendish, M. acuminata, and M. paradisiaca). Tyrosinase from the pulps was extracted, purified, immobilized, and characterized. Thereafter, the potentials of the immobilized tyrosinase in the possible production of l-3,4-dihydroxyphenylalanine (L-DOPA) in an improvised batch reactor was exploited using tyrosine and ascorbate as the substrates. L-DOPA production was monitored via thin-layer chromatography and spectrophotometry (Arnow's method). L-DOPA is a drug that is used in the treatment of Parkinson's disease. Hence, this study exploited a non-chemical route for its synthesis using the tyrosinase obtained from the banana pulps. The purified tyrosinase had an optimum pH and temperature of 6.5 and 7.0, respectively. The molecular weight of the purified tyrosinase was 45 kDa. Quercetin and resorcinol both competitively inhibited the purified tyrosinase from the three cultivars. Immobilized M. cavendish tyrosinase produced the highest concentration (0.60 mM) of L-DOPA after 8 h in an improvised batch reactor. The tyrosinase in the banana pulps serves as a cheap and readily available green route for the possible production of L-DOPA.
Keywords: L-dopa; Tyrosinase; banana pulp; batch reactor; immobilization.