L- Dopa production of Physarum polycephalum under different cultivation conditions

Abstract

L-DOPA is an amino acid that plays a key role in the treatment of Parkinsonism. However, chemically synthesizing L-DOPA has some disadvantages such as low enantiomeric, low conservation rate and high cost. Therefore, many approaches have been researched for biological sources of LDOPA. There has been one research in L-DOPA production from slime molds, which found a dark-spored (Stemonitis herbica) could produce 50 mg of L-DOPA from only 1g to 1.5g fresh fruiting bodies. The aim of this study is to investigate the effects of some factors such as light and culture types (solid vs liquid culture) on L-DOPA production of P. polycephalum (another dark-spored slime mold, which can grow well in synthetic media) by Thin-layer Chromatography (TLC) and High-performance Liquid Chromatography (HPLC). Physarum polycephalum was cultured in six different conditions, including both solid and liquid medium with different light exposed treatments. The light used was LED light, with the output of 2880 Lm and wavelength range from 380nm to 780 nm. The biomass of P. polycephalum and L-DOPA content and production were analyzed and compared. The best condition for biomass production is 5 days old liquid culture in complete dark, which yielded 12 (g/L) dried biomass. In contrast, the condition that produced has the lowest biomass is the treatment of solid medium kept 4 days in the dark and 1 day of light, which yielded only 3 (g/L) dried biomass. Overall, light can have negative effects on P. polycephalum growth; liquid culture seems superior to solid culture. Initially, TLC was applied with all the samples for the detection of L-DOPA and the result suggested the presence of the compound in all samples with the Rf value was around 0.64. HPLC quantification found out that the highest L-DOPA content (1.05 mg/g) was found in the biomass obtained from the solid culture kept in the dark for 4 days and 1-day of light exposure. It also led to the conclusion that light has positive affect to L-DOPA production, and the best condition for cultivation is solid medium with the treatment of light as stressed condition. However, it should be noted that the L-DOPA production (g/L) depends on the L-DOPA content in the biomass and the biomass production.