Facing with worldwide problem, extreme weather such as drought, flooding, and cold wave which is caused by global warming, renewable energy has gotten lots of interests. Among the various kinds of renewa-ble energy, microalga based biofuel is considered as future energy, because it is renewable, carbon neutral, no-competitive in food problem, and equal for all country where there are water and sun. However, algal bio-fuel needs more improvements in biomass and lipid productivity, and this depends on the performance of cultivation. Therefore, cultivation was studied using various kinds of methods to enhancing their perfor-mance and economic feasibility. In order to achieve these goals, I tested microalgae cultivation by using or-ange peel waste. Orange peel waste is the largest waste from juice manufacturing facility, so it is already con-centrated. In addition to that, after the juice squeezing process, they still have lots of nutrients like saccha-rides, phosphate, amino acid and so on. Orange peels have long been used as cattle feed in form of pellet with low price, so it needs development in additional value. Furthermore, orange peel from juice manufacturing factory is clean and familiar with people, therefore it has more salability in human edible valuable nutrient like DHA or phytochemicals.
In this study, I have done these three experiments.
First of all, I treated orange peels with various pretreatment processes to achieve as much as algae ed-ible nutrients. Considering the economic nutrients and biodiesel production, I tested optimum ratio of orange peel and solvent, and aqueous extraction time in room temperature without any acid/base addition. In addi-tion, to achieve more amount of nutrient, aqueous extraction using autoclave was also adapted. With the results from this step, I made two types of orange peel extract to cultivate microalgae for producing biofuels and value added chemicals.
Secondly, I conducted mixotrophic cultivation of Chlorella vulgaris OW-01 to produce biofuel. In order to cultivate Chlorella vulgaris, I optimized pH and concentration of nitrate, and conducted compara-tive cultivation with ordinary medium. Cells cultivated in orange peel extraction had 4 times more biomass and FAME productivity, and even more, they had better quality of biodiesel.
In third, I conducted heterotrophic cultivation of Aurantiochytrium sp. KRS101 to produce more val-ue added DHA with biofuel. Optimization of pH, N source, concentration of nitrate, and added amount of glucose was conducted. 1.2 g/L NaNO3 added orange peel extract showed the best ratio between output DHA yield and input glucose and fructose even compared with high-cost ordinary basal medium.
As a result, orange peel was perfectly used as nutrient source for algal cultivation using the quizzing and pellet manufacturing process which is included in previous juice production process Heterotrophic of Aurantiochtyrium showed better biomass, FAME yield than mixotrophic cultivation of Chlorella vulgaris. And considering the produced amount of orange peel from juice manufacturing facilities in U.S. is estimated upto 0.62 MMT per year, and this amount can be calculated to 3.1 MMT OPE medium, 13.64 kMT dry bio-mass of Aurantiochytrium sp., and 6.57 kMT FAME with 1.95 kMT DHA. It seems that the amount of pro-duced DHA using OPE can substitute 42% of previous DHA production from microalgae and this production could make additional $148 million.