| Transforming food waste into value-added products is a forward-looking approach to the growing global problem of food waste management.Microalgae have been used as cell factories for the study of metabolites related to industrial and biomedical applications because of their ability to grow sustainably from marginal resources.Microalgae have been used as cell factories for research and production of metabolites related to industrial and biomedical applications because of their ability to grow sustainably well.Therefore,food waste to be used as the potential feedstock in biological process for microalgae cultivation is a win-win strategy for relieving global environmental burdens and also achieving valorized conversion from waste to wealth.The focus of this study is:Algal biochar was used to purify,adsorb and recycle waste medium of microalgae;The hydrolysis system of food waste?staple food?was established to investigate the feasibility of using food waste hydrolysate as the only nutrient source of dunaliella.The two-stage culture strategy of dunaliella biomass and carotenoid accumulation was developed by optimizing the culture conditions?hydrolysate concentration and LED light source?.Expand the culture scale of dunaliella in fermenter and analyze the economic feasibility;Finally,based on the research results,this paper also carried out research expansion.The main conclusions are as follows:?1?Algal biochar can be used to improve the treatment of waste medium and improve its regeneration efficiency.Moreover,the adsorption effect of 3%biochar on the waste medium is the best,which can not only absorb the algae debris in the water,but also have a small impact on the salinity of the water.?2?The waste medium after biochar treatment can be recycled for dunaliella culture.By combining the growth effect of microalgae and the amount of biochar,the waste medium treated with 3%biochar was most suitable for the culture of dunaliella.?3?In the hydrolysate,the carbohydrate recovery rate of hydrolysate was 82.7%,and the recovery of phosphorus and nitrogen were 4.5 mg g-1and 3.5 mg g-1,respectively.Compared with the purified carbon source,the algae biomass of the hydrolysate and biochar treatment group could reach 3.1 g L-1,which was similar to the glycerol group.These results indicated that food waste hydrolysate was suitable as the only nutrient source to culture microalgae.?4?The concentration of hydrolysate had obvious difference on the biomass accumulation,but had little effect on the accumulation of carotenoids.The optimum concentration of glycosaccharide hydrolysate to promote the growth of Dunaliella salina was 10 g L-1and the biomass(2.93 g L-1)and biomass productivity(0.22 g L-1d-1)of low light treatment to 12 days were relatively highest;The change trend of microalgae PDS was similar in the groups treated with different hydrolyzate concentrations,indicating that the induced glycolysis rate was similar.?5?Blue light has potential stimulatory effect on biomass accumulation,which is better than white light and red light.The highest biomass and productivity were obtained in the treatment group with blue light and hydrolysate concentration of 10(3.7 g L-1and 0.3 g L-1d-1,respectively).?6?Blue light promotes the accumulation of biomass more than red and white light,and it has a potential stimulating effect on biomass accumulation.In the treatment group with blue light and hydrolysate-10,its biomass and productivity values were the highest(3.7 g L-1and 0.3 g L-1d-1,respectively).?7?Through the optimization of hydrolysate concentration and LDE,a two-stage strategy was developed.The results showed that the use of low blue light in the first stage could promote the accumulation of biomass,high blue light in the second stage could promote the accumulation of?-carotene,and high red light could promote the synthesis of lutein.?8?The two-stage culture strategy was used to expand the culture on a large scale in a fermenter,and the biomass was about 4.1 g L-1;Compared with the shaking flasks culture,the exponential period was shortened to 8 days,saving 4 days.When treated with blue light,the yield of beta carotene could reach 11.5 mg L-1and d-1.the yield of lutein could be harvested up to 8.5 mg L-1d-1under red light treatment.?9?A economic cost analysis was conducted on the coordination of food waste hydrolysates with algal biochar to promote the accumulation of biomass and carotenoids.2.73 kg of biochar and 150 g food waste were needed for biosynthesis of12 g?-carotene and 9 g lutein.?10?The feasibility of using food waste as a nutrient source of microalgae was further verified by expanding the research by changing the species of microalgae and the source of food waste.The results showed that chlorella could efficiently produce lipids and lutein from food waste?bread?in a semi-continuous fermentation system.In summary,this study showed that the utilization of food waste combined with the high-value products of microalgae can promote the biomass and carotenoid accumulation,so as to realize the nutrification,reduction,harmlessness and recycling of waste.These findings provide technical guidance to use this strategy for microalgae commercial scale production,and it also provides a new way to solve the problem of global waste combined with microalgae biological refining. |
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