Chemical functionalization is an effective approach to address interfacial deterioration caused by environmental exposure in cellulose nanofiber(CNF)-epoxy nanocomposites.However,how functionalization affects interfac...Chemical functionalization is an effective approach to address interfacial deterioration caused by environmental exposure in cellulose nanofiber(CNF)-epoxy nanocomposites.However,how functionalization affects interfacial deterioration and durability of nanocomposites in erosive environment is still lacked.In this work,the global mechanical properties and local interfacial intermolecular behavior of pristine and functionalized CNF-reinforced nanocomposites are investigated through molecular dynamics simulations.The results show that functionalization can enhance the interfacial energy barrier and debonding stress by 43%and 57%,respectively.Functionalized CNF inhibits the slippage of epoxy chains,ensuring better interfacial adhesion and efficient stress transfer between fiber and matrix.Functional groups promote the formation of interfacial bridging and topological structures and weaken the hydrogen bonding ability of water molecules,leading to stronger intermolecular adsorption effect and better interfacial integrity.The epoxy molecular configuration evolution and intermolecular interactions,caused by the functionalization of CNF in the interfacial region,enhance the interfacial erosion resistance,contributing to the durability of the nanocomposites.This study reveals the in-depth interfacial deterioration mechanism of functionalized nanocomposites under erosive environment,inspiring a novel strategy for the design of durable CNF-reinforced nanocomposites.展开更多
Increasing the self-resistance levels of Streptomyces is an effective strategy to improve the production of antibiotics.To increase the oxytetracycline(OTC) production in Streptomyces rimosus,we investigated the coope...Increasing the self-resistance levels of Streptomyces is an effective strategy to improve the production of antibiotics.To increase the oxytetracycline(OTC) production in Streptomyces rimosus,we investigated the cooperative effect of three co-overexpressing OTC resistance genes:one gene encodes a ribosomal protection protein(otrA) and the other two express efflux proteins(otrB and otrC).Results indicated that combinational overexpression of otrA,otrB,and otrC(MKABC) exerted a synergetic effect.OTC production increased by 179%in the recombinant strain compared with that of the wild-type strain M4018.The resistance level to OTC was increased by approximately two-fold relative to the parental strain,thereby indicating that applying the cooperative effect of self-resistance genes is useful to improve OTC production.Furthermore,the previously identified cluster-situated activator OtcR was overexpressed in MKABC in constructing the recombinant strain MKRABC;such strain can produce OTC of approximately7.49 g L^((-1)),which represents an increase of 19%in comparison with that of the OtcR-overexpressing strain alone.Our work showed that the cooperative overexpression of self-resistance genes is a promising strategy to enhance the antibiotics production in Streptomyces.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFF0500802)the National Science Fund for Distinguished Young Scholars(No.52025081)+2 种基金Key Research and Development Program of Guangdong Province(No.2019B111107001)Shenzhen Science and Technology Programs(No.RCBS20200714114819352)Foundation for Distinguished Young Talents in Higher Education of Guangdong(No.2021KQNCX096).
文摘Chemical functionalization is an effective approach to address interfacial deterioration caused by environmental exposure in cellulose nanofiber(CNF)-epoxy nanocomposites.However,how functionalization affects interfacial deterioration and durability of nanocomposites in erosive environment is still lacked.In this work,the global mechanical properties and local interfacial intermolecular behavior of pristine and functionalized CNF-reinforced nanocomposites are investigated through molecular dynamics simulations.The results show that functionalization can enhance the interfacial energy barrier and debonding stress by 43%and 57%,respectively.Functionalized CNF inhibits the slippage of epoxy chains,ensuring better interfacial adhesion and efficient stress transfer between fiber and matrix.Functional groups promote the formation of interfacial bridging and topological structures and weaken the hydrogen bonding ability of water molecules,leading to stronger intermolecular adsorption effect and better interfacial integrity.The epoxy molecular configuration evolution and intermolecular interactions,caused by the functionalization of CNF in the interfacial region,enhance the interfacial erosion resistance,contributing to the durability of the nanocomposites.This study reveals the in-depth interfacial deterioration mechanism of functionalized nanocomposites under erosive environment,inspiring a novel strategy for the design of durable CNF-reinforced nanocomposites.
基金supported by funding from Shengxue Dacheng Pharmaceutical Co.,Ltd,National Natural Science Foundation of China(31400034 and 31570031)the Ministry of Science and Technology of China(2013CB734001)
文摘Increasing the self-resistance levels of Streptomyces is an effective strategy to improve the production of antibiotics.To increase the oxytetracycline(OTC) production in Streptomyces rimosus,we investigated the cooperative effect of three co-overexpressing OTC resistance genes:one gene encodes a ribosomal protection protein(otrA) and the other two express efflux proteins(otrB and otrC).Results indicated that combinational overexpression of otrA,otrB,and otrC(MKABC) exerted a synergetic effect.OTC production increased by 179%in the recombinant strain compared with that of the wild-type strain M4018.The resistance level to OTC was increased by approximately two-fold relative to the parental strain,thereby indicating that applying the cooperative effect of self-resistance genes is useful to improve OTC production.Furthermore,the previously identified cluster-situated activator OtcR was overexpressed in MKABC in constructing the recombinant strain MKRABC;such strain can produce OTC of approximately7.49 g L^((-1)),which represents an increase of 19%in comparison with that of the OtcR-overexpressing strain alone.Our work showed that the cooperative overexpression of self-resistance genes is a promising strategy to enhance the antibiotics production in Streptomyces.
