title: Effects of cytoplasm and reactant polarities on acid-catalyzed lipid transesterification in wet microalgal cells subjected to microwave irradiation.
abstract: The polarities of the cytoplasm and reactants were measured through dielectric spectroscopy, contact angle test, NMR, and FTIR to investigate the mechanisms underlying acid-catalyzed lipid transesterification in wet microalgal cells subjected to microwave irradiation. Organics with apolar functional groups in the cytoplasm decreased the contact angle of methanol against triglyceride by 13.92°, which subsequently increased transesterification efficiency by 2.4 times. The microalgal biomass, given its higher hydrophilicity index of 1.96 than lipids, was more accessible to hydrophilic alcohols, which subsequently promoted transesterification. Water in the cytoplasm promoted the dielectric constant of methanol and increased the contact angle of methanol against triglyceride by 20.51°, which subsequently decreased transesterification efficiency by 72.6%. The inhibitory effect of water on transesterification weakened with the prolonged carbon lengths of the alcohols because of decreased polarity. Microwave decreased the electric constants of alcohols and reduced the polarity difference between alcohols and lipids, thereby improving transesterification efficiency.
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China. Electronic address: juncheng@zju.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
authors.forename: Junhu
authors.initials: J
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
authors.forename: Kefa
authors.initials: K
authors.lastname: Cen
mesh_terms: D018533:Biomass; D002384:Catalysis / Q000187:drug effects; D002708:Chlorella / Q000166:cytology / Q000187:drug effects / Q000528:radiation effects; D003593:Cytoplasm / Q000378:metabolism*; D004560:Electricity; D004574:Electromagnetic Fields; D004951:Esterification / Q000187:drug effects; D005227:Fatty Acids / Q000378:metabolism; D008055:Lipids / Q000737:chemistry*; D000432:Methanol / Q000494:pharmacology; D058086:Microalgae / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects*; D008872:Microwaves; D014280:Triglycerides / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D005227:Fatty Acids; D008055:Lipids; D014280:Triglycerides; D014867:Water; D000432:Methanol
keywords: Cytoplasm; Microwave irradiation; Polarity; Transesterification; Wet microalgal cell