Study On Microbial Lipid Fermentation Of Trichosporon Cutaneum Under High Saline Stress

Microbial lipid is the best alternative of animal and vegetable lipid feedstock for the production of aviation fuel and biodiesel.Microbial lipid fermentation requires a large amount of fresh water,resulting in the heavy burdens of fresh water usage and subsequent wastewater treatment pressure,which is one of the main obstacles affecting its industrial application potential.Utilization of high saline seawater or industrial wastewater for microbial lipid fermentation is an important alternative to reduce the freshwater consumption.Saline tolerance and toxin biodegradability of microorganism is required to use high saline water for microbial lipid fermentation.Previous studies found that Trichosporon cutaneum is a robust oleaginous yeast strain with strong environmental adaptability and degradation ability of toxic substance.In this thesis,the oleaginous yeast T.cutaneum was used for the experimental study on microbial lipid fermentation under seawater and saline wastewater.Microbial lipid fermentation in different seawater salinities and saline tolerance of T.cutaneum was studied at the first part of this thesis.Firstly,saline tolerance of T.cutaneum ACCC20271 was investigated.It was found that it can tolerate up to 130 g/L of NaCl after a long-term adaptive evolution and has the potential to grow in high saline osmotic pressure.Secondly,T.cutaneum was cultured in several typical salinities to investigate the capacity of lipid production,including the salinity of textile and electrodialysis wastewater(1.0%),major marine seawater salinity(3.5%),the salinity of seawater in tropical desert climate and petrochemical wastewater(4.4%)and the salinity of tanneries and pharmaceutical wastewater(6.0%).The results showed that the typical salinity(3.5%)had no negative effect on microbial lipid accumulation,while higher salinities inhibited lipid accumulation.Finally,T.cutaneum MP11 was used to research the capacity of microbial lipid production in high saline conditions.It was found that the typical salinity(3.5%)promoted the microbial lipid accumulation of T.cutaneum MP11,and its lipid production(31.7 g/L)was about 36%higher than that of fresh water(23.3 g/L).The results show that high saline water has the potential to replace fresh water for microbial lipid fermentation.In addition,an important phenomenon was observed that T.cutaneum MP11 can be spontaneously stratified in the fermentation broth under high saline conditions,and the oleaginous yeast cells gathered on the upper layer of the fermentation broth,which is of great significance for lipid recovery.In the second part of this thesis,microbial lipid production of T.cutaneum MP11 was investigated under industrial wastewater with high saline.Industrial wastewater contains aromatic compounds,antibiotics and other pollutants.Phenol is one of the commonly existing organic pollutants in various industrial wastewater.T.cutaneum MP11 was to be tolerant to 1,000 mg/L of phenol at the typical salinity.Therefore,microbial lipid fermentation was carried out in high saline water with 1,000 mg/L of phenol.The results indicate that lipid production of T.cutaneum MP11 in this conditions was close to that of the fresh water without phenol(23.6 g/L vs 23.3 g/L),and more than 80%of phenol was degraded.Finally,microbial lipid fermentation was carried out in tetracycline and pickled wastewater.The results show that tetracycline had no negative effect on the lipid production of T.cutaneum,and there was a certain amount of lipid accumulation in pickled wastewater without adding any nutrients.This results indicate that T.cutaneum MP11 has a potential for wastewater treatment.