嗜热菌——工业用酶的新来源

综述了嗜热菌和极端嗜热菌产生的热稳定性的淀粉酶、纤维素酶、环糊精酶、木聚糖酶、几丁质酶、葡萄糖异构酶、蛋白酶等的研究进展及其在食品、化工、环保等方面的应用前景。     

Genomic and mechanistic insights into the biodegradation of organic pollutants

Several new methodologies have enabled recent studies on the microbial biodegradation mechanisms of organic pollutants. Culture-independent techniques for analysis of the genetic and metabolic potential of natural and model microbial communities that degrade organic pollutants have identified new metabolic pathways and enzymes for aerobic and anaerobic degradation. Furthermore, structural studies of the enzymes involved have revealed the specificities and activities of key catabolic enzymes, such as dioxygenases. Genome sequencing of several biodegradation-relevant microorganisms have provided the first whole-genome insights into the genetic background of the metabolic capability and biodegradation versatility of these organisms. Systems biology approaches are still in their infancy, but are becoming increasingly helpful to unravel, predict and quantify metabolic abilities within particular organisms or microbial consortia.     

Biodegradation of natural and synthetic rubbers: A review

Since polymeric materials do not decompose easily, disposal of waste polymers is a serious environmental concern. Widespread studies on the biodegradation of rubbers have been carried out in order to overcome the environmental problems associated with rubber waste. This report provides an overview on the microbial degradation of natural and synthetic rubbers. Rubber degrading microbes, bacteria and fungi, are ubiquitous in the environment especially soil. The qualitative data like plate assay, scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and Sturm test indicated that both natural and synthetic rubbers can be degraded by microorganisms. It has confirmed that the enzymes latex clearing protein (Lcp) and rubber oxygenase A (RoxA) are responsible for the degradation of natural and synthetic rubbers. Lcp was obtained from Gram-positive bacterium Streptomyces sp. strain K30 and RoxA from Gram-negative bacterium Xanthomonas sp. strain 35Y. Analysis of degradation products of natural and synthetic rubbers indicated the oxidative cleavage of double bonds in polymer backbone. Aldehydes, ketones and other carbonyl groups were detected as degradation products from cultures of various rubber degrading strains. This review emphasizes the importance of biodegradation in environmental biotechnology for waste rubber disposal.     

Microbial degradation of halogenated aromatics: molecular mechanisms and enzymatic reactions

Halogenated aromatics are used widely in various industrial, agricultural and household applications. However, due to their stability, most of these compounds persist for a long time, leading to accumulation in the environment. Biological degradation of halogenated aromatics provides sustainable, low-cost and environmentally friendly technologies for removing these toxicants from the environment. This minireview discusses the molecular mechanisms of the enzymatic reactions for degrading halogenated aromatics which naturally occur in various microorganisms. In general, the biodegradation process (especially for aerobic degradation) can be divided into three main steps: upper, middle and lower metabolic pathways which successively convert the toxic halogenated aromatics to common metabolites in cells. The most difficult step in the degradation of halogenated aromatics is the dehalogenation step in the middle pathway. Although a variety of enzymes are involved in the degradation of halogenated aromatics, these various pathways all share the common feature of eventually generating metabolites for utilizing in the energy-producing metabolic pathways in cells. An in-depth understanding of how microbes employ various enzymes in biodegradation can lead to the development of new biotechnologies via enzyme/cell/metabolic engineering or synthetic biology for sustainable biodegradation processes.     

Biological degradation of plastics: a comprehensive review

Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.     

Biodegradation of halogenated organic compounds.

In this review we discuss the degradation of chlorinated hydrocarbons by microorganisms, emphasizing the physiological, biochemical, and genetic basis of the biodegradation of aliphatic, aromatic, and polycyclic compounds. Many environmentally important xenobiotics are halogenated, especially chlorinated. These compounds are manufactured and used as pesticides, plasticizers, paint and printing-ink components, adhesives, flame retardants, hydraulic and heat transfer fluids, refrigerants, solvents, additives for cutting oils, and textile auxiliaries. The hazardous chemicals enter the environment through production, commercial application, and waste. As a result of bioaccumulation in the food chain and groundwater contamination, they pose public health problems because many of them are toxic, mutagenic, or carcinogenic. Although synthetic chemicals are usually recalcitrant to biodegradation, microorganisms have evolved an extensive range of enzymes, pathways, and control mechanisms that are responsible for catabolism of a wide variety of such compounds. Thus, such biological degradation can be exploited to alleviate environmental pollution problems. The pathways by which a given compound is degraded are determined by the physical, chemical, and microbiological aspects of a particular environment. By understanding the genetic basis of catabolism of xenobiotics, it is possible to improve the efficacy of naturally occurring microorganisms or construct new microorganisms capable of degrading pollutants in soil and aquatic environments more efficiently. Recently a number of genes whose enzyme products have a broader substrate specificity for the degradation of aromatic compounds have been cloned and attempts have been made to construct gene cassettes or synthetic operons comprising these degradative genes. Such gene cassettes or operons can be transferred into suitable microbial hosts for extending and custom designing the pathways for rapid degradation of recalcitrant compounds. Recent developments in designing recombinant microorganisms and hybrid metabolic pathways are discussed.     

聚乙烯塑料生物降解研究进展

聚乙烯(polyethylene,PE)塑料是全球通用合成树脂中产量最丰富的品种，也是最难降解的塑料之一，其在环境中大量积累已造成严重的生态污染。传统的垃圾填埋、堆肥和焚烧处理技术难以满足生态环境的保护要求，生物降解是解决塑料污染问题的一种生态友好、成本低廉、前景可期的方法。本文对PE塑料的化学结构、降解微生物的种类、降解酶和代谢途径等方面进行了综述，结合国内外PE塑料生物降解的前沿和热点问题，建议重点开展高效降解菌株筛选、人工合成菌群构建、降解酶的挖掘与改造等方面的研究，为PE塑料生物降解研究提供路径选择和理论借鉴。     

聚乳酸(PLA)生物降解的研究进展

聚乳酸(Polylactic Acid,PLA)是一种新兴的,由可再生资源--乳酸聚合而成的高分子聚酯.因为其具有优良的物理化学性能、生物相容性及生物可降解性,且对环境及人体无毒害作用,而被认为是一种最具潜力的绿色生物塑料.作为环境友好材料,聚乳酸日益受到人们的重视.基于可循环利用的考虑,其生物降解的研究也成为当前研究的一个重要方面.本文综述了PLA生物降解领域的相关进展,包括降解的微生物学、相关酶学及分子生物学,系统阐述了PLA可能的生物降解机制.并对生物系统处理PLA废弃物的可行性进行了探讨.     

聚对苯二甲酸乙二醇酯生物降解的研究进展

塑料广泛存在于人类的日常生活中，在给人们生活带来便利的同时，大量塑料废物也给环境带来很大压力。聚对苯二甲酸乙二醇酯(polyethylene terephthalate, PET)是一种以石油为原料的高分子热塑性材料，因其具有耐用、透明度高、重量轻等特性，已成为世界上使用最广泛的塑料之一。由于PET具有结构复杂以及难降解的特性，可在自然界中长期存在，不仅对全球生态环境造成严重的污染，而且已经威胁到人类健康。如何对PET废弃物进行降解已成为全球的难题之一，相较于物理法和化学法，生物降解法是目前处理PET废弃物最为绿色环保的方法。本文分别介绍了微生物和生物酶对PET生物降解的研究现状、PET的生物降解途径、PET生物降解机制以及PET降解酶的分子改造等方面的研究，并对如何实现PET的高效降解、寻找和改造可降解高结晶度PET的微生物或酶进行展望，为PET的生物降解微生物或酶的有效开发应用提供理论依据。     

A review of plastic waste biodegradation

With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.     

Advances in the field of high‐molecular‐weight polycyclic aromatic hydrocarbon biodegradation by bacteria

Interest in understanding prokaryotic biotransformation of high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs) has continued to grow and the scientific literature shows that studies in this field are originating from research groups from many different locations throughout the world. In the last 10 years, research in regard to HMW PAH biodegradation by bacteria has been further advanced through the documentation of new isolates that represent diverse bacterial types that have been isolated from different environments and that possess different metabolic capabilities. This has occurred in addition to the continuation of in-depth comprehensive characterizations of previously isolated organisms, such as Mycobacterium vanbaalenii PYR-1. New metabolites derived from prokaryotic biodegradation of four- and five-ring PAHs have been characterized, our knowledge of the enzymes involved in these transformations has been advanced and HMW PAH biodegradation pathways have been further developed, expanded upon and refined. At the same time, investigation of prokaryotic consortia has furthered our understanding of the capabilities of microorganisms functioning as communities during HMW PAH biodegradation.     

微塑料与土壤环境中微生物互作研究进展

作为环境中广泛存在的污染物,微塑料(microplastics)的相关研究备受关注。基于已有研究,本文综合分析了微塑料与土壤微生物(soil microorganisms)的互作关系,微塑料会通过直接或间接的方式影响微生物群落结构与多样性,影响的程度取决于微塑料的类型、剂量和形状。土壤微生物会通过形成表面生物膜和群落选择效应来适应微塑料这一外来物所引起的变化。本文还特别关注了微塑料的生物降解机理,同时探究了影响这一过程的因素,微生物首先会定殖在微塑料表面,分泌多种胞外酶在特定位点发挥作用,将聚合物转化成低聚物或单体,解聚的小分子进入胞内进一步分解代谢,而影响这一降解过程的因素除了分子量、密度、结晶度等微塑料自身理化性质,还包括一些生物因素和非生物因素对相关微生物生长代谢和酶活性的作用。未来研究应注重与实际环境的联系,在深入探究微塑料生物降解研究的同时,开发解决微塑料污染问题的新技术。     

塑料生物降解检测方法的研究进展

塑料处理不当造成的污染问题已成为全球性难题。目前的解决办法除回收利用与使用可生物降解塑料替代之外,最主要途径仍是寻求高效的塑料降解方法。其中,采用微生物或酶处理塑料的方法因其具有条件温和、不产生次生环境污染的优势而受到越来越多的关注。塑料生物降解技术的核心是高效解聚微生物/酶,然而当前的分析检测方法无法满足塑料生物降解资源的高效筛选,因此开发准确、快速的塑料降解过程分析方法,对于生物降解资源筛选和降解效能评价具有重要意义。本文介绍了近年来在塑料生物降解领域的常用分析检测技术,包括高效液相色谱、红外光谱、凝胶渗透色谱以及透明圈测定等,重点讨论了荧光分析策略在快速表征塑料生物降解过程中的应用,为进一步规范塑料生物降解过程的表征与分析研究,以及开发更高效的塑料生物降解资源筛选方法提供借鉴。     

A Review of Plastic Waste Biodegradation

ABSTRACT

With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.     

FTIR-spectroscopic studies of the fine structure of nitrocellulose treated by Desulfovibrio desulfuricans

Most studies have concluded that nitrocellulose (NC) with high degree of nitrogen content is resistant to biodegradation. Our results demonstrated that NC (>11%N) does undergo biotransformation in the presence of sulfate-reducing bacteria Desulfovibrio desulfuricans 1388. FTIR analyses indicated that the substitution of nitro groups for OH(-) groups took place. The spectrum of precipitate obtained after acetone extraction of NC resembled mainly the spectrum of native cellulose. Thus the synthetic unbiodegradable polymer was transformed to the natural compound accessible for microorganisms.     

Modification of cell surface properties of <Emphasis Type="Italic">Pseudomonas alcaligenes</Emphasis> S22 during hydrocarbon biodegradation

Biodegradation of water insoluble hydrocarbons can be significantly increased by the addition of natural surfactants one. Very promising option is the use of saponins. The obtained results indicated that in this system, after 21 days, 92% biodegradation of diesel oil could be achieved using Pseudomonas alcaligenes. No positive effect on the biodegradation process was observed using synthetic surfactant Triton X-100. The kind of carbon source influences the cell surface properties of microorganisms. Modification of the surface cell could be observed by control of the sedimentation profile. This analytical method is a new approach in microbiological analysis.     

聚乳酸的生物降解

聚乳酸(polylactic acid, PLA)因其良好的理化性能、生物相容性和生物降解性而备受关注，已被认为是石油基塑料最具潜力的替代者，但在实际应用中仍然存在降解缓慢循环周期长的问题，因此对PLA的生物降解深入研究对于解决塑料垃圾污染和缓解能源危机至关重要。近年来，有关微生物(放线菌、细菌和真菌)和酶(蛋白酶、脂肪酶、酯酶和角质酶)降解PLA的研究已经取得了一定的进展。本文从降解微生物、降解酶和降解机制等方面综述了PLA生物降解的研究进展，并展望了PLA生物降解研究未来的发展趋势。     

The environment,microbes and bioremediation: microbial activities modulated by the environment

Microorganisms in nature are largely responsible for the biodegradation and removal of toxic and non-toxic chemicals. Many organisms are also known to have specific ecological niches for proliferation and colonization. The nature of the environment dictates to a large extent the biodegradability of synthetic compounds by modulating the evolutionary processes in microorganisms for new degradative genes. Similarly, environmental factors often determine the extent of microbial gene expression by activating or repressing specific gene or sets of genes through a sensory signal transduction process. Understanding how the environment modulates microbial activity is critical for successful bioremediative applications.     

Degradation of xenobiotic compounds in situ: Capabilities and limits

Abstract: Exploiting microorganisms for remediation of waste sites is a promising alternative to groundwater pumping and above ground treatment. The objective of in situ bioremediation is to stimulate the growth of indigenous or introduced microorganisms in regions of subsurface contamination, and thus to provide direct contact between microorganisms and the dissolved and sorbed contaminants for biotransformation. Subsurface microorganisms detected at a former manufactured gas plant site contaminated with coal tars mineralized significant amounts of naphthalene (8–43%) and phenanthrene (3–31%) in sediment-water microcosms incubated for 4 weeks under aerobic conditions. Evidence was obtained for naphthalene mineralization (8–13%) in the absence of oxygen in field samples. These data suggest that biodegradation of these compounds is occurring at the site, and the prospects are good for enhancing this biodegradation. Additional batch studies demonstrated that sorption of naphthalene onto aquifer materials reduced the extent and rate of biodegradation, indicating that desorption rate was controlling the biodegradation performance.     

Recent advances in biodegradation in China: New microorganisms and pathways,biodegradation engineering,and bioenergy from pollutant biodegradation

We are facing serious environmental challenges, and environmental biotechnology is an enabling technology to reduce or eliminate pollution. In recent years, environmental pollution in China has been receiving great attention, and this paper provides an up-to-date review on progress in biodegradation research in China. This progress includes the isolation of extremophilic microorganisms for pollutant degradation in extreme conditions and the study of genes and enzymes related to biodegradation pathways. Biodegradation engineering has potential as an interesting and powerful platform, where genetic engineering, process engineering, and signal transduction engineering are applied together. In addition, pollutant treatment combined with the production of renewable sources of bioenergy by microorganisms is attractive.