The kinetics of asymmetric production of R-（-）-mandelic acid （R-MA） from phenylglyoxylic acid （PGA） catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of...The kinetics of asymmetric production of R-（-）-mandelic acid （R-MA） from phenylglyoxylic acid （PGA） catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of glucose and PGA were controlled respectively with a dual feeding system. When the electron donor glucose was supplied at the rate of 0.0833mmol·gdw^-1·h^-1, the specific production rate （qp） and the enantiomeric excess of R-MA reached the maximum 0.353mmol·gdw^-1·h^-1 and 97.1%, respectively. The apparent reduction activity of yeast FD 11 b was obviously affected by both substrate PGA and product MA. The qp value reached the maximum 0.36-0.38mmol·gdw^-1·h^-1 when the PGA concentration was controlled between 25 and 35mmol·L^-1. The obvious substrate inhibition of bioconversion was observed at the PGA concentrations higher than 40mmol·L^-1. The accumulation of product MA also caused a severe feed-back inhibition for its production when the product concentration was above 60mmol·L^-1. The kinetic model with the inhibition effect of both substrate and product was simulated by a computer-based least-square arithrnatic. The established kinetic model was in good agreement with the experimental data.展开更多
Effective coverage and protection is a priority in wound treatment.Collagen and chitosan have been widely used for wound dressings due to their excellent biological activity and biocompatibility.Silver nanoparticles(A...Effective coverage and protection is a priority in wound treatment.Collagen and chitosan have been widely used for wound dressings due to their excellent biological activity and biocompatibility.Silver nanoparticles(AgNPs)have a powerful antibacterial effect.In this study,a macromolecular and small-molecular collagen mixed solution,a macromolecular and small-molecular chitosan mixed solution were prepared,and a silver nanoparticle-loaded collagen-chitosan dressing(AgNPCCD)has been proposed.First,the effects of a collagen-chitosan mixed solution on the proliferation of human umbilical vein endothelial cells and the secretion of cytokines were evaluated.Then,the characteristics and antibacterial effects of the AgNP-CCD were tested,and the effects on wound healing and the influence of wound cytokine expression were investigated via a deep second-degree burn wound model.The results showed that at the proper proportion and concentration,the collagen-chitosan mixed solution effectively promoted cell proliferation and regulated the levels of growth factors(vascular endothelial growth factor[VEGF],epidermal growth factor[EGF],plateletderived growth factor[PDGF],transforming growth factor[TGF-b1],basic fibroblastic growth factor[bFGF])and inflammatory factors(TNF-α,IL-1β,IL-6,IL-8).Moreover,AgNP solutions at lower concentrations exerted limited inhibitory effects on cell proliferation and had no effect on cytokine secretion.The AgNP-CCD demonstrated satisfactory morphological and physical properties as well as efficient antibacterial activities.An in vivo evaluation indicated that AgNP-CCD could accelerate the healing process of deep second-degree burn wounds and played an important role in the regulation of growth and inflammatory factors,including VEGF,EGFL-7,TGF-β1,bFGF,TNF-α and IL-1β.This AgNP-CCD exerted excellent biological effects on wound healing promotion and cytokine expression regulation.展开更多
Wounds may remain open for a few weeks in severe burns,which provide an entry point for pathogens and microorganisms invading.Thus,wound dressings with long-term antimicrobial activity are crucial for severe burn woun...Wounds may remain open for a few weeks in severe burns,which provide an entry point for pathogens and microorganisms invading.Thus,wound dressings with long-term antimicrobial activity are crucial for severe burn wound healing.Here,a sandwich structure composite wound dressing anchored with silver nanoparticles(AgNPs)was developed for severe burn wound healing.AgNPs were in situ synthesized on the fibers of chitosan nonwoven fabric(CSNWF)as the interlayer of wound dressing for sustained release of silver ion.The firmly anchored AgNPs could prevent its entry into the body,thereby eliminating the toxicity of nanomaterials.The outer layer was a polyurethane membrane,which has a nanoporous structure that could maintain free transmission of water vapor.Chitosan/collagen sponge was selected as the inner layer because of its excellent biocompatibility and biodegradability.The presence of AgNPs in the CSNWF was fully characterized,and the high antibacterial activity of CSNWF/AgNPs was confirmed by against Escherichia coli,Pseudomonas aeruginosa and Staphylococcus aureus.The superior wound healing effect on deep dermal burns of presented composite wound dressing was demonstrated in a porcine model.Our finding suggested that the prepared AgNPs doped sandwich structure composite wound dressing has great potential application in severe wound care.展开更多
基金Supported by the Natural Science Foundation of Fujian Province (No.E0310019) and Key Project of Science and Technology of Fujian Province (No.2003H023).
文摘The kinetics of asymmetric production of R-（-）-mandelic acid （R-MA） from phenylglyoxylic acid （PGA） catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of glucose and PGA were controlled respectively with a dual feeding system. When the electron donor glucose was supplied at the rate of 0.0833mmol·gdw^-1·h^-1, the specific production rate （qp） and the enantiomeric excess of R-MA reached the maximum 0.353mmol·gdw^-1·h^-1 and 97.1%, respectively. The apparent reduction activity of yeast FD 11 b was obviously affected by both substrate PGA and product MA. The qp value reached the maximum 0.36-0.38mmol·gdw^-1·h^-1 when the PGA concentration was controlled between 25 and 35mmol·L^-1. The obvious substrate inhibition of bioconversion was observed at the PGA concentrations higher than 40mmol·L^-1. The accumulation of product MA also caused a severe feed-back inhibition for its production when the product concentration was above 60mmol·L^-1. The kinetic model with the inhibition effect of both substrate and product was simulated by a computer-based least-square arithrnatic. The established kinetic model was in good agreement with the experimental data.
基金supported by the Fujian Burn Medical Center([2017]171)the Key Clinical Specialty Discipline Construction Programme of Fujian,China([2012]149)+2 种基金the Key Project of Fujian Provincial Department of Science and Technology,China(2014Y0056)the Joint Funds for the Innovation of Science and Technology,Fujian,China(2017Y9027)the Fujian Provincial Key Laboratory of Burn and Trauma,China.
文摘Effective coverage and protection is a priority in wound treatment.Collagen and chitosan have been widely used for wound dressings due to their excellent biological activity and biocompatibility.Silver nanoparticles(AgNPs)have a powerful antibacterial effect.In this study,a macromolecular and small-molecular collagen mixed solution,a macromolecular and small-molecular chitosan mixed solution were prepared,and a silver nanoparticle-loaded collagen-chitosan dressing(AgNPCCD)has been proposed.First,the effects of a collagen-chitosan mixed solution on the proliferation of human umbilical vein endothelial cells and the secretion of cytokines were evaluated.Then,the characteristics and antibacterial effects of the AgNP-CCD were tested,and the effects on wound healing and the influence of wound cytokine expression were investigated via a deep second-degree burn wound model.The results showed that at the proper proportion and concentration,the collagen-chitosan mixed solution effectively promoted cell proliferation and regulated the levels of growth factors(vascular endothelial growth factor[VEGF],epidermal growth factor[EGF],plateletderived growth factor[PDGF],transforming growth factor[TGF-b1],basic fibroblastic growth factor[bFGF])and inflammatory factors(TNF-α,IL-1β,IL-6,IL-8).Moreover,AgNP solutions at lower concentrations exerted limited inhibitory effects on cell proliferation and had no effect on cytokine secretion.The AgNP-CCD demonstrated satisfactory morphological and physical properties as well as efficient antibacterial activities.An in vivo evaluation indicated that AgNP-CCD could accelerate the healing process of deep second-degree burn wounds and played an important role in the regulation of growth and inflammatory factors,including VEGF,EGFL-7,TGF-β1,bFGF,TNF-α and IL-1β.This AgNP-CCD exerted excellent biological effects on wound healing promotion and cytokine expression regulation.
基金supported by the National Natural Science Foundation of China(31800796)the Nature Sciences Funding of Fujian Province(2019J01238)the Fuzhou University Testing Fund of Precious Apparatus(2021T018).
文摘Wounds may remain open for a few weeks in severe burns,which provide an entry point for pathogens and microorganisms invading.Thus,wound dressings with long-term antimicrobial activity are crucial for severe burn wound healing.Here,a sandwich structure composite wound dressing anchored with silver nanoparticles(AgNPs)was developed for severe burn wound healing.AgNPs were in situ synthesized on the fibers of chitosan nonwoven fabric(CSNWF)as the interlayer of wound dressing for sustained release of silver ion.The firmly anchored AgNPs could prevent its entry into the body,thereby eliminating the toxicity of nanomaterials.The outer layer was a polyurethane membrane,which has a nanoporous structure that could maintain free transmission of water vapor.Chitosan/collagen sponge was selected as the inner layer because of its excellent biocompatibility and biodegradability.The presence of AgNPs in the CSNWF was fully characterized,and the high antibacterial activity of CSNWF/AgNPs was confirmed by against Escherichia coli,Pseudomonas aeruginosa and Staphylococcus aureus.The superior wound healing effect on deep dermal burns of presented composite wound dressing was demonstrated in a porcine model.Our finding suggested that the prepared AgNPs doped sandwich structure composite wound dressing has great potential application in severe wound care.
