Yifeng Tao

Using imidazolium-based ionic liquids as dual solvent-catalysts for sustainable synthesis of vitamin esters: inspiration from bio- and organo- catalysis†

Vitamin E (VE) has significant biological activities and thus its acylation to increase its stability is of extreme interest. We developed an efficient and sustainable approach using imidazolium-based ionic liquids as dual solvent-catalysts for the esterification between α-tocopherol (the most active form of VE) and succinic anhydride. Although in literature it is reported that lipase can catalyze this reaction, hereby we demonstrate that the reaction observed in DMSO and DMF is catalyzed by the histidyl residues of the protein. Histidine and its analogue containing an imidazole ring were tested as organocatalysts for the production of α-tocopherol succinate. In light of the imidazole organocatalysis, commercially-available 3-alkyl-1-methyl imidazolium ILs [CnC1Im][X−] were investigated as dual solvent-catalysts for the esterification of α-tocopherol with succinic anhydride, and provided satisfactory yields and reaction rates. [C5C1Im][NO3−] can be recycled by water extraction, instead of organic solvent extraction to separate α-tocopherol succinate from [C5C1Im][NO3−], with an average yield of 94.1% for 4 subsequent batches, while the catalytic activity of the recycled ILs showed almost no loss after 4 batches. The developed protocol for the synthesis of α-tocopherol esters and IL recycling bears industrial potential due to the ease of use and the efficient recycling.

Synergistic effects of amine and protein modified epoxy-support on immobilized lipase activity

We have developed an improved and effective method to immobilize Yarrowia lipolytica lipase Lip2 (YLIP2) on an epoxy poly-(glycidylmethacrylate-triallyisocyanurate-ethyleneglycoldimethacrylate) (PGMA-TAIC-EGDMA) support structure with or without amine or/and protein modifications. Our results show that there is an increase in the activity of the immobilized lipase on n-butylamine (BA) modified support (420U/g support) and the biocompatible gelatin modified support (600U/g support) when compared to the support without modification (240U/g support). To further study the influences of BA and gelatin modification on the activity of the immobilized lipase, gelatin and BA were concurrently used to decorate the support structure. Lipase immobilized on 2% BA/gelatin (1:1) modified support obtained the highest activity (1180U/g support), which was five-fold higher than that on a native support structure. These results suggest that the activity of a support-immobilized lipase depends on the support surface properties and a moderate support surface micro-environment was crucial for elevated activity. Collectively, these data show that a combined gelatin and BA modification regulates the support surface more suitable for immobilizing YLIP2.

Enhancing trimethylolpropane esters synthesis through lipase immobilized on surface hydrophobic modified support and appropriate substrate feeding methods.

Candida sp. 99-125 lipase immobilized on surface hydrophobic modified support and appropriate substrate feeding methods were used to improve the synthesis of tri-substituted trimethylolpropane (TMP) esters, which can be used as raw materials for biodegradable lubricants. The proposed novel production method is environmentally friendly. Lipase was adsorbed on surface hydrophobic silk fibers that were pretreated by amino-modified polydimethylsiloxane. A 5-level-4-factors central composite model, including reaction time, temperature, enzyme amount, and molar ratio of fatty acid to TMP, was designed to evaluate the interaction of process variables in the enzymatic esterification. The water activity was kept constant using a LiCl-saturated salt solution. Under the optimum conditions with 30% enzyme amount and substrates molar ratio 8.4 at 45°C for 47h, the total conversion of caprylic acid is 97.3% and the yield of tri-substituted TMP esters is 95.5%. The surface hydrophobic treatment resulted in less cluster water accumulated on the surface immobilized lipase, which was demonstrated by near-infrared spectra. Consequently, the optimum temperature and water tolerance of immobilized lipase were increased. Two TMP-feeding methods were used to maintain high molar ratio of fatty acid to TMP, and increase the final tri-substituted TMP esters content exceeding 85% (w/w) in reactant.

Improving performance of Yarrowia lipolytica lipase lip2-catalyzed kinetic resolution of (R, S)-1-phenylethanol by solvent engineering

Abstract Extracellular Yarrowia lipolytica lipase Lip2 (YLIP2) demonstrated an (R)-enantiopreference for efficient resolution of (R,S)-1-phenylethanol by solvent engineering with different kinds of binary solvent. The enantioselectivity was significantly improved by the addition of 1, 4-dioxane. The reaction parameters including co-solvent concentration, reaction temperature, and the reaction time were optimized. When the reaction was carried out with n-hexane in the presence of 0.8% 1,4-dioxane at 50°C for 72 h, the enantiomeric excess of product markedly increased to 99.1% from 66% in pure n-hexane; the enantiomeric ratio was higher than 200, which was 500-fold compared with that in pure n-hexane. The results indicated that it is very important to design the proper co-solvents, especially to create appropriate micro-environment for YLIP2 for catalyzing the resolution of (R,S)-1-phenylethanol.

A water-dependent kinetics guide for complex lipase-mediated synthesis of biolubricants in a water activity control reactor

A water-dependent kinetic model for a lipase-mediated reaction with multiple substrates and products in a water activity control reactor was developed. Solvent-free esterification of trimethylolpropane (TMP), the products of which can be used as biolubricants, was investigated using a lipase from Candida sp. 99–125 as catalyst under variable water activities in a 5 L batch stirred tank reactor. Water activity control was accomplished at the set point by introduction of dry air through the reaction medium at a digital feedback-controlled flow rate. For the cases of esterification of TMP, long-term (>72 h) control of water activity resulted in a considerable improvement of yield. By introducing progressive water removal and combining principles with an intrinsic kinetic model of the Ping-Pong Bi-Bi mechanism, the integrated model can predict both the forward and reverse rates for TMP reactions. Kinetic parameters depending on the water activity were estimated by nonlinear regression fitting of experimental data. The proposed approach not only enables optimization of the reaction under defined conditions, but also provides a solution for industrial upscaling of similar environmentally friendly biocatalytic processes.

Synthesis of 2-ethyl hexanol fatty acid esters in a packed bed bioreactor using a lipase immobilized on a textile membrane

Abstract An enzymatic process using a packed bed bioreactor with recirculation was developed for the scale-up synthesis of 2-ethylhexyl palmitate with a lipase from Candida sp. 99–125 immobilized on a fabric membrane by natural attachment to the membrane surface. Esterification was effectively performed by circulating the reaction mixture between a packed bed column and a substrate container. A maximum esterification yield of 98% was obtained. Adding molecular sieves and drying the immobilized lipase both decreased the water content at the reactor outlet and around the enzyme, which led to an increase in the rate of esterification. The long-term stability of the reactor was tested by continuing the reaction for 30 batches (over 300 h) with an average esterification yield of about 95%. This immobilized lipase bioreactor is scalable and is thus suitable for industrial production of 2-ethylhexyl palmitate.

Bioconversion of Biomass to Bulk Chemicals

Due to the current forces of sustainable production and available bioconversion technologies for biomass, the routes of biomass conversion to bulk chemicals are expected to make a significant effect on the production of bulk chemicals within 10 years. Biobased bulk chemicals, especially biofuels and biomaterials, possess a clear substitution potential of fossil oil-based bulk chemicals. Biofuels including bioethanol, biobutanol, etc., have appeared as an alternative and attractive candidate for fighting with the climate change and potential energy issue. Biobased monomers such as isoprene, 1,3-propanediol, lactic acid, etc., for biomaterials aim at making up the insufficient supplies of fossil-based monomers. Biotechnologies providing the tools for modifying and reprogramming the microorganisms and the integration of global engineering technologies will considerably accelerate the development of eco-efficient processes and products.