Phosphatidylcholine Adsorbed On Modified Silica With Trace Hydrophobic Groups To Produce Phosphatidylserine

Phosphatidylserine?PS?,as a natural rare phospholipid,is widely used in medical and food health care.It is usually prepared by phospholipase D?PLD?in a water-organic phase reaction system for biocatalysis;but the large amount of organic solvents makes it impossible to guarantee the safety of the product.Therefore,it is very necessary to construct a pure water medium system for the preparation of rare phospholipids.In this paper,two methods are used to construct a pure water medium system to catalyze the synthesis of PS using PLD.First,silica gel was modified by different silane coupling agents to obtain a functional carrier.The silane coupling agent on the surface of the carrier was used as the"anchor"point to directly adsorb PC in a pure aqueous medium.The adsorption process was systematically studied,the adsorption kinetic model was established and related parameters were calculated.PC-adsorbed carriers were used as the substrate and the transphosphatidylation reaction was carried out in the aqueous phase,the PS was successfully synthesized.The surface of the carrier can not only disperse the substrate phospholipid,but also the reaction phase interface of the enzymatic reaction.After the reaction,the product obtained was eluted and separated using coconut oil as an eluent and prepared into a microcapsule product.The production process from raw materials to products was completed.In order to avoid the production consumption of bioenzyme catalyst and reduce the production cost and improve the production efficiency.This paper proposes a new water-solid reaction system.The covalent binding method is used to fix the specific concentration PLD on the surface of the carrier to form an"anchor"point for adsorption.The enzyme protein consisted of a large number of asymmetric hydrophobic residues.The self-hydrophobic effect enables adsorption of the substrate PC,and then,PS was successfully prepared by phosphatidyl transfer reaction.This article mainly explores the effects of enzyme protein immobilization rate on PC adsorption and PS preparation.This reaction system not only effectively improves the reaction efficiency and selectivity,and avoids the use of toxic and harmful reagents.In addition,the immobilization technology can realize the recovery of PLD,improve the production efficiency,reduce the production cost,and avoid the catalyst on the final product pollution.The main experimental results are as follows:?1?The silane coupling agents OTMS,DTMS,HDTMS,APTMS,HGPTMS and EGPTMS were used to modify the silica gel.The obtained modified silica was employed for the adsorption of PC.The results showed when EGPTMS-modified silica with 5×10^-9mol/g was used,the maximum adsorption performance was obtained and reached 2.65×10^-6mol/m²(0.5g _PC/g_sillica).Meanwhile,the highest yield of PS reached 99%.In addition,the modified carrier still showed good stability after reused for 20 batches.The silane coupling agent did not fall off or leak.After the reaction,the product PS were eluted by coconut oil.The coconut oil solution containing PS was microencapsulated with chitosan?the degree of deacetylation for 95%?as the wall material to obtain a product with good coating performance and uniform particle size distribution.?2?The one-step and two-step adsorption model of PC on the surface of silica gel were established using silica gel modified by silane coupling agents HDTMS and EGPTMS as carriers,respectively.Through the model,the adsorption process of PC on the surface of modified silica gel was clarified.The correlation coefficients for the proposed one-step adsorption model are all greater than 0.97,indicating that the proposed adsorption model represented the adsorption process;then,two-step adsorption model is proposed basing on the one-step adsorption model.The experimental results show that the maximum adsorption density of PC reached 7.51×10^-6mol/m²on the modified supports.The Gibbs free energy of PC adsorption on the two carriers were-19.8 and-14.7 k J/mol,respectively.They were less than 19.5 k J/mol which was the Gibbs free energy of PC forming micelles in the water phase.This indicates that the adsorption process can be carried out spontaneously without external energy.The PS was synthesized at different PC adsorption density conditions.The PS yield was over 98%when the adsorption amount was less than half of the saturated adsorption.When increase the adsorption density,PC formed a multi-layer on the surface of the carrier.On the other hand,the decrease in the yield also proved the correlation degree of the adsorption model established in this experiment from the experimental point of view.?3?In order to solve the difficulty of recovering free enzymes and increase the reuse activity in the water-solid phase reaction process,the PLD molecule was covalently bound on the surface of carriers at the specific concentration to make adsorption of PC and transphosphatidylation carry out simultaneously.The protein molecule played a role as"anchors"to provide the hydrophobic affinity with phospholipids due to its much functional groups.The experimental results are as follows:The best immobilized loading of PLD was 0.17 mg_protein/g_silica;the added amount of immobilized PLD was 80 mg?wet?;the reaction temperature was 35°C;p H was 6.0;the highest yield of PS reached 95%.In addition,the fluidized bed reactor was used to investigate the continuous reaction process conditions of PS.After 10 cycles with the fluidization rate of 3 ml/min,the yield of PS reached 98%,which might provide the theoretical guidance for the industrial production.