Improved degradation of azo dyes by lignin peroxidase following mutagenesis at two sites near the catalytic pocket and the application of peroxidase-coated yeast cell walls

• Mutations in Lignin peroxidase Trp171 environment improved azo dyes degradation. • Expression on yeast cell surface and cell lysis allowed reusability of biocatalyst. • Aga2-LiP chimeric variants were characterized. The enzymatic degradation of azo dyes is a promising alternative to ineffective chemical and physical remediation methods. Lignin peroxidase (LiP) from Phanerochaete chrysosporium is a heme-containing lignin-degrading oxidoreductase that catalyzes the peroxide-dependent oxidation of diverse molecules, including industrial dyes. This enzyme is therefore ideal as a starting point for protein engineering. Accordingly, we subjected two positions (165 and 264) in the environment of the catalytic Trp171 residue to saturation mutagenesis, and the resulting library of 10⁴ independent clones was expressed on the surface of yeast cells. This yeast display library was used for the selection of variants with the ability to break down structurally-distinct azo dyes more efficiently. We identified mutants with up to 10-fold greater affinity than wild-type LiP for three diverse azo dyes (Evans blue, amido black 10B and Guinea green) and up to 13-fold higher catalytic activity. Additionally, cell wall fragments displaying mutant LiP enzymes were prepared by toluene-induced cell lysis, achieving significant increases in both enzyme activity and stability compared to a whole-cell biocatalyst. LiP-coated cell wall fragments retained their initial dye degradation activity after 10 reaction cycles each lasting 8 h. The best-performing mutants removed up to 2.5-fold more of each dye than the wild-type LiP in multiple reaction cycles.     

TIE技术在某化工厂废水毒性原因鉴别中的应用

运用美国水生生物毒性鉴别评价技术对组分相对复杂的某化工厂废水进行毒性原因鉴别。结果表明：导致该厂废水毒性的关键污染物是二萘酚,对硝基氯苯和间硝硝基氯苯。对ＴＩＥ技术在中国推广的实用性,可行性以及应用前景等进行了讨论。     

A review on the production of fermentable sugars from lignocellulosic biomass through conventional and enzymatic route—a comparison

The scarcity of fossil fuels has urged the economically developed countries to find the resources for an alternative energy sources. In apprehension to this, biofuels, like bioethanol and biobutanol, produced from lignocellulosic biomass were considered as potential alternative. There are several methods for the pretreatment of biomass before it is being used as a feedstock for the production of fermentable sugars. However, one of the crucial concerns here is to enumerate an economic pretreatment scheme that can be implemented in large scale for the production of mostly exposed cellulosic part from biomass. This will ensure an effective hydrolysis of cellulose for the production of fermentable sugars and the production of biobutanol from these derived sugars. Moreover, the keynote understanding of an effective fermentation is the production of less inhibitory compounds like furfural, hydroxymethyl furfural during the hydrolysis of cellulose. Enzymatic hydrolysis of cellulose was reported as the most efficient method is this aspect. Trichoderma sp. was found the mostly used resources for the enzyme called cellulase and Aspergillus sp. for hemicellulase enzymes. The most crucial part here is the isolation of proper enzyme that will increase the rate of hydrolysis. Moreover, selection of proper pretreatment process will be a key benefit to the production of fermentable sugars through enzymatic hydrolysis. Based on the biomass nature, the evaluated hot water pretreatment followed by enzymatic hydrolysis with a provision of enzyme reusability (like encapsulated or enzyme separation with membrane) seems to be promising for enhanced biofuel-production.     

Impact of undissociated volatile fatty acids on acidogenesis in a two-phase anaerobic system

This study investigated the degradation and production of volatile fatty acids(VFAs)in the acidogenic phase reactor of a two-phase anaerobic system.20 mmol/L bromoethanesulfonic acid(BESA)was used to inhibit acidogenic methanogens(which were present in the acidogenic phase reactor)from degrading VFAs.The impact of undissociated volatile fatty acids(un VFAs)on"net"VFAs production in the acidogenic phase reactor was then evaluated,with the exclusion of concurrent VFAs degradation."Net"VFAs production from glucose degradation was partially inhibited at high un VFAs concentrations,with 59%,37% and 60% reduction in production rates at 2190 mg chemical oxygen demand(COD)/L undissociated acetic acid(un HAc),2130 mg COD/L undissociated propionic acid(un HPr)and 2280 mg COD/L undissociated n-butyric acid(un HBu),respectively.The profile of VFAs produced further indicated that while an un VFA can primarily affect its own formation,there were also un VFAs that affected the formation of other VFAs.     

Influence of amendments on soil arsenic fractionation and phytoavailability by Pteris vittata L

Increasing availability of soil arsenic is of significance for accelerating phytoremediation efficiency of As-polluted sites. The effects of seven amendments, i.e., citrate, oxalate, EDTA, sodium polyacrylate (SPA), phosphate rock (PR), single superphosphate (SSP), and compost on fractionation and phytoavailability of soil As were investigated in lab culture experiment. The results showed that the addition of PR, SPA, EDTA or compost to soils significantly increased the concentration of NaHCO₃-extractable As over a 120 d incubation period compared with the control (amendment-free) soil. Then, the four amendments were selected to add to As-contaminated soil growing Pteris vittata. It was concluded that As accumulation by the fern increased significantly under the treatments of PR and SPA by 25% and 31%, respectively. For As fractionation in soil, SPA increased Fe-As significantly by 51% and PR increased Ca-As significantly by 18%, while both the two amendments reduced occluded-As by 16% and 19%, respectively. Adding PR and SPA in soil increased the activities of urease and neutral phosphatase resulting from the improvement the fertility and physical structure of the soil, which benefits plant growth and As absorption of P. vittata. The results of the research revealed that both PR and SPA were effective amendments for improving phytoremediation of As-contaminated sites by P. vittata.     

Preparation of antibodies and development of an enzyme immunoassay for determination of atrazine in environmental samples

An indirect competitive enzyme-linked immunosorbent assay (ELISA) has been developed and optimized for atrazine determination in soil at different depths (0–10, 10–20, and 20–30 cm) before and after 48 h of application, corn shoot and cow milk samples collected from Dina farm, Egypt. This assay was based on a specific polyclonal antibodies (PAb) raised by immunizing New Zealand rabbits with an immunogen prepared by coupling 3-{4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine-2-yl} thiopropanoic acid to bovine serum albumin (BSA) via N-hydroxysuccinimide (NHS) active ester method. The sensitivity (estimated as IC₅₀value) was 17.5 μg mL^?1 with a detection limit of 0.1 ng mL^?1. The maximum atrazine concentration was found in soil especially in the deepest layer (325 and 890 μg kg^?1 before and after application, respectively). Atrazine concentration in corn shoot was 333.28, μg kg^?1 dry plant, while there was no detectable amount in milk. All samples screened by ELISA were validated by gas chromatography mass spectrometer procedure (GC/MS). Good correlation was achieved between the two methods (r = 0.997 for soil and 0.9814 for plant). This study demonstrates the utility and convenience of the simple, practical and cost–effective ELISA method in the laboratory for analysis of environmental samples. The method is ideal for the rapid screening of large numbers of samples in laboratories where access to GC/MS facilities, is limited or lacking.     

Inductive potency of TCDD, TBDD and three 2,3,7,8-mixed-halogenated dioxins in liver microsomes of male rats. Enzyme kinetic considerations

The enzyme inducing potency of single doses of three 2,3,7,8-substituted mixed halogenated dibenzo-p-dioxins was investigated and compared with 2,3,7,8-TCDD and 2,3,7,8-TBDD. All substances showed a quite similar potency for EROD induction. The use of a substrate concentration of 0.5 μM ethoxyresorufin is strongly recommended.     

中小型钩锻件的一火成形与模具设计

一火成形是中小型模锻的发展方向,它既能提高锻件质量、模具寿命,又能提高生产效率、降低成本、便于管理。此文以船用集装箱紧固钩锻件为例,就其一火成形的工艺及模具设计进行分析、讨论,重点介绍其工艺步骤、模具设计方案及要求。     

消灭火炬防治大气污染

长岭炼油化工总厂改造火炬系统时采用先进技术，如二级压缩机技术、变频调速技术、新型无烟火炬头以及自动点火器系统，对火炬系统的含硫污水进行密闭处理等。改造后正常生产时不点火炬，事故放空时能及时点燃火炬。     

逼近于理想解的排序方法在环境质量评价中的应用

本文将多目标决策中的逼近于理想解排序方法,引入到环境质最评价之中,并提出确定污染物指标权重的方法。最后,结合浦东新区内河水质评价,验证其准确性和优越性。