Effects Of Light On Growth And Pigments Production By Monascus Purpureus

Light is a crucial signal for development and physiological processes in filamentous fungi.Different wavelengths of monochromatic,including red,yellow,green,blue,near UV can regulate culture morphology,mycelium,spore formation and secondary metabolism.Effects of different wavelength light(red,yellow,green and blue)on culture morphology,mycelium,spore formation and intracellular pigments that named monascin(MS),ankaflavin(AK),rubropunctamine(RUM),monascorubramine(MOM),rubropunctatin(RUN)and monascorubrin(MON)production of Monascus purpureus M9 were investigated in this study.Red light was most effective in inducing the pigments production and growth of Monascus purpureus M9.When exposed to red light,the colonies with profuse growth of aerial mycelia that were longer and denser and high yields of pigments were discovered.Compared with darkness,the emergence of dark red was earlier and the proportion of it became larger.Many radial fold appeared early and significantly.The total quantity of spores was observably stimulated under red light,especially the number and rate of cleistothecia.The content of RUM,MOM,AK,RUN and MON exposed to continuous red light were increased by 7.8%,17.3%,11.1%,15.6%,11.4%and 16.6%,respectively.Various red light intensities,illumination times and rhythm on six well known pigments production and citrinin production were examined,and the optimal illumination time was 30 min/d,the optimal illumination intensity was 300 lux,and the optimal illumination rhythm was 12 h.Furthermore,on the basis of Box-Behnken experimental design,the optimal illumination condition of MS and AK production was as follows:illumination time 30 min/d,illumination intensity 300 lux,illumination rhythm 12 h.The optimal production of MS was 26.77±0.38 mg/g,and increased by 42.6%compared to the darkness,the optimal production of AK was 13.12±0.12 mg/g,and increased by 62.6%.The pigments and citrinin production under different red light conditions were investigated,and we found that the trend of production of RUM,MOM,MS and AK was 300 30(12)>300 45(18)>400 45(12)>400 30(18)>D.However,the production of RUN and MON was D>400 30(18)>400 45(12)>300 45(18)>300 30(12),the trend of production of citrinin was similar to that of two orange pigments.Yields of RUM and MOM were increased by 53.8%and 75.2%,MS and AK were increased by 42.2%and 59.4%,RUN and MON were decreased by 42.6%and 54.5%,citrinin were decreased by 42.5%under the optimal red light illumination condition 300 30(12).The effects of red light on Monascus pigments and citrinin biosynthetic gene cluster were analyzed by RT-qPCR.Asscciated with the production of pigments and citrinin production,we found that the expression levels of mppA/B/D/F,mppR1/R2,MpPKS5,MpFasA2/B2 biosynthetic genes were positively correlated with the production of orange pigments,and the expression levels of mppC and mppE were positively correlated with the yields of red and yellow pigments.In combination with citrinin production,the production of citrinin increased along with the increase of ctnA/D/E/F/G/H/I,orf1/3/4/5,pksCT expression levels and decrease of ctnR1 expression levels.In the study,the results showed that ctnA/D/E/F/G/H/I,orf1/3/4/5,pksCT were positively correlated with citrinin production,thus,ctnR1 was negatively correlated with citrinin production.