| Fucoxanthin,also known as fucoxanthin,is an allenes carotenoid with strong antioxidant properties and has unique physiological activities in anti-inflammatory,anti-cancer,anti-diabetic,anti-obesity,liver-protection and other physiological functions.At present,commercial fucoxanthin is mainly obtained from large brown algae,but there are problems of low fucoxanthin content,thick cell wall and excessive alginate,which makes the cost of extraction and purification is too high and the purity of the product is low.Marine diatom Phaeodactylum tricornutum has the advantages of high growth rate,high fucoxanthin content and artificial large-scale cultivation.It is easy to extract and obtain high-quality fucoxanthin products,which is considered as algae-based one of the best sources of fucoxanthin.This paper systematically explored the characteristics of P.tricornutum growth and fucoxanthin accumulation in photo-fermentation system.First,the mixotrophic culture conditions were optimized in the shaking flask system;then the main process parameters were optimized in the 5L photo fermentation,and the key technology of photo-fermentation in P.tricornutum was constructed.The effects of the supplementary nitrogen in batchs and two-stage culture strategy on the growth of P.tricornutum and the yield of fucoxanthin were studied,and the key technology system for production fucoxanthin in P.tricornutum by photo-fermentation was constructed.The main experimental results were as follows:1.In 250 m L shaking flask system,the effects of various factors on the growth and fucoxanthin accumulation of P.tricornutum under mixotrophy were studied.The results showed the highest biomass(3.87 g/L),fucoxanthin content(14.45 mg/g)and yield(53.32 mg/L)were obtained under the conditions of 80 mg/L sodium dihydrogen phosphate and 6.30 mg/L ferric chloride by culturing for 12 days,compared with those before optimization(sodium dihydrogen phosphate 10 mg/L,ferric chloride3.15 mg/L)increased by 20.94%,75.36%and 145.26%,respectively(p<0.01).2.In 250 m L shaking flask system,the effects of the supplementary nitrogen and carbon in batchs on the growth of P.tricornutum and the production of fucoxanthin were explored.The results showed that under the condition of the total nitrogen content unchanged at 0.02 mol/L,supplementing nitrogen source(urea+tryptone,1:1,N mol/N mol)in 6 batchs and carbon source(glycerol,0.1 mol/L)in one-time culturing for 12 days,the highest content(17.06 mg/g)and yield(48.39 mg/L)of fucoxanthin were obtained,which are 44.33%and 96.39%higher than the supplementing nitrogen source in one-time,respectively(p<0.01).3.In the 5 L photo-fermentation system,the effects of initial light intensity,nitrogen source types and concentration and different light qualities on the growth of P.tricornutum and the production of fucoxanthin were explored.The results show that under the condition of the initial light intensity of 100μmol/m~2/s,0.02 mol/L mixed nitrogen source(urea+tryptone,1:1,N mol/N mol),red and blue mixed light(R:G:B=70.9:18.3:10.9)culturing for 10 days by photo-fermentation,the biomass,content and yield of fucoxanthin were 3.80 g/L、13.44 mg/g and 47.02 mg/L,compared with the conditions of initial light intensity of 20μmol/m~2/s,0.02 mol/L mixed nitrogen source,natural white light(R:G:B=19.7:76.3:4.0)increased by 40.74%,32.68%and104.97%,respectively(p<0.01).4.In the 5 L photo-fermentation system,the effects of supplementing nitrogen in batchs and two-phase culture with different light qualities on the growth of P.tricornutum and the production of fucoxanthin were verified.The results showed that under the condition of supplementing 0.02 mol/L mixed nitrogen source(urea+tryptone,1:1,N mol/N mol)in 6 batchs culturing for 10 days,the biomass,content and yield of fucoxanthin increased to 4.15 g/L,18.22 mg/g and 71.40 mg/L,respectively,which were significantly higher than the result of supplementing nitrogen source in one-time(p<0.05).Under two-phase culture by supplementing blue light(adding 25%blue light,R:G:B=67.1:16.7:16.3,185μmol/m~2/s)in the later stage(7.5～10 d)culturing for 10 days,the fucoxanthin content reached the maximum value of 19.62 mg/g,which was 7.68%higher than that without supplementing blue light(p<0.05). |
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