Showing papers in "Progress in Industrial Microbiology in 2002"

Bioremediation of compounds hazardous to health and the environment: An overview

Abstract: Publisher Summary This chapter focuses on the fundamental microbial mechanisms (oxidative, reductive, and hydrolytic reactions) and associations in plant and microbial populations (competition, cross-feeding and commensalism), which may be essential to their success. Bioremediation of the chemicals in the soil depends on the activities of microbes in the soil, or in association with the root system. Chemical/physical properties of the chemical itself can influence the availability of the chemical to the microbe, or the susceptibility to degradative processes. Molecular alterations catalyzed by the microbial processes include oxidation, reduction, hydrolysis, de-esterification, dehalogenation, dealkylation, conjugation, and others. These processes usually result in a non-toxic chemical in the case of a pesticide, or in decreasing contamination levels of hazardous materials. Dissipation of pesticides in the soil involves several processes: volatilization, photodecomposition, leaching, adsorption, and microbial degradation. This chapter has been an overview of bioremediation processes, together with a few examples to illustrate the principles and efficacy of those processes.

Biodegradation of fuel oils and lubricants: Soil and water bioremediation options

Abstract: Publisher Summary A controlled or directed bioremediation process seeks to provide an accelerated natural decomposition, and in this chapter discusses the best practice to attempt to achieve this goal. Bio degradative clean up of oil contaminated soils, sediments, and waters has only recently been considered a viable clean up option. The detailed studies of the effects of different types of clean up strategy on the coastal regions around Prince William Sound, contaminated by the Exxon Valdiz crude oil spill in 1989, revealed that of all the approaches the best results were obtained where natural processes were allowed to occur. However, the rates of oil removal were slow and in some cases could have lead to an extended exposure of marine species to toxic hydrocarbons and intermediates of biodegradation. Micro-organisms are capable of utilizing hydrocarbons as a carbon and energy source.

Microbial variables for bioremediation of heavy metals from industrial effluents

Abstract: Publisher Summary Bioremediation is an economically feasible and technically efficient technology for metal removal/recovery. It can comfortably fit into the metal treatment processes and is eco-friendly in nature. This is because not all the companies that generate metal-polluted wastewater will have the capability or the interest to do anything other than the basic treatment to comply with the legislation. Hence to overcome this, what is needed is a series of specialists, centralized facilities that would be capable of removing metal from the wastewater and regenerating or processing the metal-loaded sorbent, and then converting the recovered metal into reusable form. Alternatively, if the biosorbent used is a waste product, its incineration could be used to produce metal rich slag. Looking into the economic feasibility, in terms of scale-up and working efficiency as a technology, the “microbial biosorbents” provide encouraging results to be utilized in wastewater treatment. What is needed is an extra mural input from the industries, generating metal-polluted wastewater to invest into such clean-up technologies before discharging their liquid effluents into the water streams.

Lignin degradation by bacteria

Abstract: Publisher Summary The complex aromatic polymer lignin comprises about 25% of the land based biomass on earth, and its recycling is a vital component of the earth's carbon cycle. Its breakdown involves multiple biochemical reactions. Though the role of fungal lignin peroxidases has been well established only in recent years, bacterial lignin degradation has gained importance. Bacteria gain access to the polymer by mechanisms, such as tunnelling, erosion, and scavenging. Bacteria of several genera such as Alcaligenes, Acinetobacter, Pseudomonas, Rhizobium, Bradyrhizobium, Bacillus, and Streptomyces readily degrade numerous lignin model compounds. Acinetobacter utilized veratrylglycerol-∼-guaiacyl ether, indulin, 2-methoxy-4-formylphenoxyacetic acid, u-conidendrin and dehydrodiisoeugenol. Plasmid-mediated dissimilation of ferulic acid and guaiacolglyceryl ether has been established in Bacillus subtilis. Cloning, sequencing, and expression of the genes involved in the dissimilation of lignin substances have been done from Bacillus subtilis to improve the degradation efficiency. The most recent advances in genetic engineering are to create potential lignin-degrading bacteria and also to elucidate the molecular mechanisms involved.

Microbial degradation of sulfur compounds present in coal and petroleum

Abstract: Publisher Summary The petroleum refining companies have recognized the fact that hydro desulfurization units for the high extent of desulfurization are extremely expensive to build and operate. Therefore, as an alternating promising method to HDS, microbial desulfurization (MDS) that harnesses the metabolic processes of suitable bacteria to the desulfurization of fossil fuels has attracted attention of many researchers. Consequently, in recent years there has been considerable effort to develop the bioprocesses for fossil fuel desulfurization. Many microbial desulfurization processes have been developed to desulfurize fossil fuels. Nevertheless, as the genes involved in the sulfur-specific metabolic pathway are identified and cloned, amplification of genes or enzymes responsible for desulfurization may lead to microbial cultures that remove organic sulfur efficiently from fossil fuels in near future. The biocatalytic desulfurization is a better option because of its low capital and operating expenses.

Lactic acid bacteria in winemaking: Influence on sensorial and hygienic quality

Abstract: Publisher Summary This chapter discusses the role of lactic acid bacteria in winemaking. The classification of enological lactic acid bacteria was established by using the conventional methods, which focus on phenotypes. According to morphological, biochemical and physiological properties, wine and grape lactic acid bacteria can be classified as lactobacilli and cocci , being either obligate and facultative heterofermentative or homofermentative. Since lactic acid bacteria are necessary to obtain malolactic fermentation, winemakers must find a solution for minimizing amine levels, even if indigenous bacteria possess decarboxylating activities. Today, a solution is the use of selected malolactic starters. O. oeni strains, free of undesirable activities, are produced and lyophilized in concentrated populations. They are massively added to wine to complete malolactic fermentation. They normally overcome the indigenous bacteria and seem to eliminate them by competition. Then after malolactic fermentation, wine is readily stabilized by sulfur dioxide, which eliminates the malolactic starter and the residual wild-type strains. It needs to know more about the ecology of micro-organisms living on grapes, how they survive on cellar equipment and how they grow in wines. Such studies were almost impossible in the past. Now the new molecular methods are opening new horizons for studying wine micro-organisms, particularly the lactic acid bacteria.

Algae-dependent bioremediation of hazardous wastes

Abstract: Publisher Summary Despite the algal diversity and relatively inexpensive algal biomass, there has been little commercial exploitation of these plants for metal removal, recovery, and prospecting. This chapter reviews algal diversity and economic importance with special reference to the processes of algal biosorption and bioaccumulation. The chapter also identifies the areas where research should concentrate in order to give to the world an “algal-based bioremediation” industry for cleaning the water bodies. Worldwide surveys indicate that the water bodies all over have been converted into dumping sites for all kinds of pollutants. The problem worsens when these polluted waters are put to uses, like irrigation. This sets in a chain of reactions, which ends up in biomagnification. Pollutants are also known to affect the growth of primary producers adversely, thus breaking the food chain at the first trophic level or at grass-root level. However, the ease with which various algae can be cultured and the variety of biomasses rendered by them as living, dead, or immobilized have made algae one of the most potent bioremediators. Though the bioremediation paradigm using algae to degrade pollutants in situ has lately attracted a lot of public attention, yet introducing the “genetically engineered” algae into the environment to enhance the process is yet to be demonstrated with success.

Microbial bioremediation of textile effluents

Abstract: Publisher Summary It is clear from this chapter that bioremediation of toxic industrial effluents by micro-organisms can be an effective method for the removal of textile effluents, and can substitute the conventional remediation processes. Broad screening of microbial biomass type should be undertaken for developing new technologies. The current consensus is that, for improved commercial use of micro-organisms, immobilization or pellet preparations in suitable carriers will prove economical for their use. In relation to other parameters of industrial relevance, micro- organisms can be highly efficient in removing the toxic components from the effluents. The nonspecific lignin-degrading system of P. chrysosporium can be significantly utilized for the aerobic degradation of heterogeneous mixture of recalcitrant dyes in wastewaters. Growing evidence indicates that lignase (lignin peroxidase) is the key lignin-degrading enzyme of this whiterot fungus, which has potential for its commercial application.

Microbial degradation of insecticides: An assessment for its use in bioremediation

Abstract: Publisher Summary In soil, micro-organisms (bacteria, fungi, etc.) are primarily responsible for pesticide degradation. Thus, the microbial breakdown of insecticides is considered to be the most important catabolic reaction in soil. Microbes are degrading xenobiotic compounds/pesticides in the environment and use them for their normal metabolic processes as carbon or phosphorus source or consume the pesticides along with other source of food or energy. This bioprocess of microbes can be utilized for the development of pesticide decontamination and restoration of health of the environment. Hydrolytic enzymes, responsible for degradation of pesticides to non-toxic products in the environment can be developed for the future remedy for toxic compounds as bioremediation. Significant proportions of insecticides may form bound residues with the soil, which are not readily available to the plants and are often not very toxic to the biota. This may represent a mechanism by which the insecticide residues may persist for longer periods in soil and may be released only very slowly, and a relatively small proportion of these may be taken up by the plants and earthworms, and are responsible for the contamination of ecosystem.

Microbial degradation of chlorobenzoates (CBAs): Biochemical aspects and ecological implications

Abstract: Publisher Summary The behavior of chlorobenzoates (CBAs) in soils and waters has been carefully considered, as these compounds are used themselves as herbicides. The Chlorobenzoic acids from mono- to tri-substituted compounds, were shown susceptible to microbial attack, even if more chlorinated isomers and/or having chlorine atoms in ortho position were demonstrated more refractory to biodegradation. CBAs can be totally mineralized with stoichiometric release of the chlorine atoms, both in aerobic and anaerobic conditions, or can undergo only co-metabolic transformations giving dead-end products, which the other microorganisms could utilize for their growth. The bacterial strategies for CBA degradation, elucidated with pure cultures or in microbial consortia, turn around the detachment of chlorine atoms that may occur through: (i) oxygenolytic elimination in an early stage mediated by more or less specific 1,2- or 1,6-dioxygenases leading to the formation of catechol or chlorocatechols; (ii) spontaneous C1-release at a later stage, by lactonization of the ortho-ring fission product; (iii) initial dehalogenation through hydrolytic or oxidative reactions with the formation of corresponding hydroxy derivatives; and (iv) reductive dechlorinations, mostly occurring in anaerobic conditions, and on polychlorinated compounds, with the formation of the corresponding derivatives carrying n-1 chlorine substituents.

Oxidation of organic and inorganic sulfur compounds by aerobic heterotrophic marine bacteria

Abstract: Publisher Summary Bacteria play important roles in both organic and inorganic sulfur transformations in the marine environment. Key component of the sulfur cycle is DMSP, perhaps the most important simple substrate that has been identified in seawater, since it contributes significantly to the bacterial carbon demand and is the main source of sulfur for bacteria in the marine environment. Thus, DMSP and its derivatives could be used for the isolation of micro-organisms that are either representatives of the bacteria in the natural environment or have potential utility for biotechnological applications. Heterotrophic sulfur oxidizers may be abundant in the marine environment, a variety of sources of reduced sulfur. Bacteria capable of heterotrophic sulfur oxidation may have an energetic advantage over those unable to obtain energy from the oxidation of inorganic sulfur. The abundance of reduced sulfur compounds and the number of heterotrophic bacteria that are isolated from the marine environment, and which oxidize inorganic sulfur, indicate that it may be a widespread phenomenon in nature. This chapter focuses on the heterotrophic bacterial transformation of organic and inorganic molecules that are commonly found in the marine environment.

Microbial degradation of polychlorinated biphenyls (PCBs) in the environment

Abstract: Publisher Summary Polychlorinated biphenyls (PCB) is an environmental pollutant, which is both difficult to quantify and difficult to remediate. Here the main degradation process in the environment— that is, the degradation by micro-organisms, is being discussed. The bioremediation of PCB is one of the most difficult tasks in the area of environmental biotechnology. The past decades brought an immense progress in biochemistry and genetics of PCB congener degradation. The stage is now set for the exploration and use of the immense microbial biodiversity, concerning PCB-degrading bacteria. In connection with the study of the activities and interactions of microbial communities using the tools developed in microbial ecology, it should be possible to identify the critical ecological parameters controlling the degradation of PCB in the environment. This knowledge-based understanding will improve considerably the in situ bioremediation of PCB-polluted site. The PCB-metabolizing activity of fungi in PCB-polluted soil and their interaction with the PCB-degrading bacteria is another unknown relationship, which should be known for a knowledge-based bioremediation strategy.

Enzymatic transformations of xenobiotics of health and environmental concern

Abstract: Publisher Summary The chapter discusses the enzymatic degradation of wide variety of xenobiotics, such as toxic, carcinogenic, teratogenic, and mutagenic compounds, which are of health and environmental concern. Microbes are omnipresent and their role in health and environmental protection is well understood. However, the understanding of the microbial enzymatic mechanisms as the detoxification strategies that form the basis for bioremediation of wastes and biological control of potentially hazardous compounds is of tremendous importance. Microbial degradation of various xenobiotics of health and environmental concern, such as nitrogenous compounds, carbamates, phenylureas, anilides, halogenated aromatic compounds, azo dyes, tannins, and heterocyclic compounds has been described. Mycotoxins in general and aflatoxins in particular have been found to be degraded by microsomal cytochrome P-450 monooxygenase and peroxidase enzymes. A microsome technology based model of detoxification strategies for health and environmental protection has been proposed.

Electro-physical properties of microbial cells during the aerobic metabolism of toxic compounds

Abstract: Publisher Summary This chapter focuses primarily with the results of the experimental studies of the effect of the aerobic metabolism of toxic compounds on the electro-physical properties of microbial cells. These studies were done by the use of the method of electro-optical analysis of cell suspensions. Works closest in theme to one, are those using electro-physical analysis to assess the damaging effect produced on microbial cells by various physico-chemical factors (including toxic compounds). They have as their main object the devising of methods for the rapid analysis of the viability of microbial cells, for the evaluation of the degree of cell injury and of the heterogeneity of cell cultures, etc. The fundamental difference between studies in the chapter and others' is that, in this chapter, microbial strains are used with enzyme systems of the initial metabolism of certain toxic compounds. During the electro-optical investigations, independent monitoring of the cellular metabolic activity toward the corresponding substrates was also performed by a number of traditional techniques.

Bioremediation of contaminated water bodies

Abstract: Publisher Summary Bioremediation of heavy metals is designed to concentrate metals in living organisms, including plant tissues, thus, minimizing the amount of solid or liquid hazardous wastes, which need to be treated and deposited at hazardous waste sites, with the ultimate goal of developing an economical method of reclaiming metals from plant residue. This will completely eliminate the need for costly off-site disposal. Bioremediation is certainly very old field, but it holds great potential. In order to realize this promise, it will be necessary to build a greater understanding of the many and varied processes that are involved. This will require a multidisciplinary approach, spanning fields as diverse as plant biology, agricultural engineering, agronomy, soil science, microbiology, and genetic engineering. However, excessive accumulation of these heavy metals can be toxic to most of the plants. The ability of certain plants to tolerate increased levels of toxic elements and their accumulation at high concentrations from various polluted environments can be exploited for the removal of toxic substances, including heavy metals from water. The use of plants for remediation of toxic substances is known as "Phytoremediation".

Bioremediation technology for environmental protection through bioconversion of agro-industrial wastes

Abstract: Publisher Summary This chapter focuses on the mushroom cultivation as one biotechnological process, which can convert the waste plant residues, rich in lignocellulosics into protein rich foods. Mushroom cultivation infact is the only microbial process or product system that can bioconvert all of the major plant polymers, such as lignin, cellulose, and hemicellulose. Utility of mushroom for bioconversion of wastes into useful fructification is well known, in addition to those for which production technology has been described in detail. Other mushrooms have also been cultivated, but their commercial cultivation is limited only to a few, which are relished by people. Most of these possess good cellulolytic and hemicellulolytic systems, and a few like Agaricus, Pleurotus, and Lentinus are also strongly lignolytic. This bioconversion is achieved through extracellular enzyme production. Detailed studies on enzyme production are needed. Strain improvement has been done, but further improvement will probably depend upon DNA technology and the use of protoplasts, combined with incorporation of novel genetic material into suitable commercial strains of mushrooms.

Biodegradation of diaryl esters: Bacterial and fungal catabolism of phenylbenzoate and some oil its derivatives

Abstract: Publisher Summary This chapter aims to provide a brief overview of the biodegradability of the diaryl ester phenylbenzoate and some of its derivatives under aerobic conditions by comparing bacterial and fungal strategies. The ability of micro-organisms to degrade the simplest diaryl ester phenylbenzoate effectively, does suggest that this structure, and most probably simple derivatives of it, can be eliminated by using biological means. However, it remains to be seen if some of the more complex compounds shown in this chapter, or similar structures, are biodegradable. Even if the basic diaryl ester structure can be hydrolyzed by micro-organisms, such as those described in this short review, the impact of substituents present on the resulting cleavage products might interfere with degradation. Therefore, more research is required to elucidate the environmental fate of these structures, and consequently, the current pure culture studies should be expanded not only to involve microbial consortia but as well extended into anaerobic systems. This will not only help to evaluate the potential environmental fate of such compounds, but furthermore such research might prove to be a rather useful tool for the development of novel structures that are biodegradable.

Degradation of natural rubber products by Nocardia species

Abstract: Publisher Summary Nocardia sp. strain 835A was shown to possess an ability to cause scissions of polymeric chains of natural rubber (NR), and the organism grew well on unvulcanized natural and synthetic isoprene rubber. Strain 835A had a high ability to colonize rubber pieces and microbial attack occurred only at points of direct contact with the colonies. A mutant strain Rc of Nocardia sp. 835A with a very high ability of disintegrating tire rubber was isolated. Disintegration of tread compounds from truck tires by strain Rc was found to be consistently influenced by the NR content. These experimental conditions gave a result with sufficient reproducibility in a relatively short time period, and the method enabled to examine various factors affecting microbial rubber degradation. It is found that the colonization of rubber pieces plays an important role in microbial decomposition of NR, and describes the unique characteristic feature of growth of the rubber-degrading organism on rubber pieces in this chapter.

Microbial transformation of aflatoxins

Abstract: Publisher Summary This chapter discusses microbial transformation of aflatoxins. The Rhizopus species degraded aflatoxin G1 (AFG1) to aflatoxin B3 (AFB3) or aflatoxicol in wheat medium. This indicated that the transformation of AFG1 occurs as a result of changes of the culture medium, or as a result of fungal growth or the action of enzymes produced during later periods of the growth cycle. Rhizopus nigricans and Saccharomyces cerevisiae effectively compete with A. parasiticus or A. flavus, when co-cultured and actually decrease growth and aflatoxin formation by the Aspergillus. S. cerevisiae retards the production of only aflatoxin G 1 without affecting aflatoxin B 1 , perhaps by producing an end product, which could have served as a metabolic repressor for aflatoxin G 1 production. The conversion activity may be cell wall or membrane bound, since the cell free extracts were not able to convert aflatoxin B1. They further postulate that these fungi are capable of oxidation and reduction of the steroid nucleus, a similar reaction with aflatoxin may be possible.

Biotransformations of tannery wastes

Abstract: Publisher Summary In general, tannins are recalcitrant molecules and are very much resistant to microbial attack because of their complexity in structure A holistic view of microbial degradation of tannins and the potential for manipulating the detannification of certain microbial strains for the beneficial effects on food, beverages, feed, and fodder are discussed Condensed tannins are more resistant than the hydrolyzable tannins, and are toxic to a variety of micro-organisms The chapter describes the biodegradation of tannins by bacteria Some bacteria, however, may also degrade many phenolic compounds, including natural ones like catechol, protocatechuic acid, etc Fifteen bacterial strains, belonging to genera Bacillus, Staphylococcus, and Klebsiella have been isolated by enrichment culture technique using tannic acid as the sole source of carbon Nine of the isolated strains grew both on tannic acid as well as on gallic acid, which are obtained upon hydrolysis, but only four strains degraded catechol or catechin Among fungi, filamentous fungi, especially the species of the genera Aspergillus and Penicillium, have been implicated in the biotransformations of tannins

Some physiological characteristics of saprotrophic and ectomycorrhizal fungi producing sporophores on the urea-treated forest floor

Abstract: Publisher Summary This chapter focuses on the physiological characteristics of the ammonia fungi and the environmental conditions under which the ammonia fungi fruit or sporulate. It begin with the reports on the occurrence of the ammonia fungi in countries other than Japan and their occurrence under natural conditions in order to show the ubiquitous characteristics of this particular fungal group. Ammonia fungi fruit or sporulate after experimental treatment of forest floor with some nitrogenous substances and also after the decomposition of dead-bodies or faeces of animals. The abilities of these fungi to grow well under alkaline conditions, to utilize a variety of nitrogenous compounds, including ammonium, nitrate, amino acids, etc., and to decompose organic matters are unique and suggestive of their role in nutrient dynamics in forest ecosystems. Hebeloma species, including both ammonia fungi and the non-ammonia fungi, utilize a variety of nitrogen compounds. This characteristic feature may be valuable for the bioremediation processes, using the mycorrhiza association between fungi and plants in the nitrogen-polluted areas.

Bioremediation of hazardous ethylenebisdithio-carbamate (EBDC) fungicides

Abstract: Publisher Summary Degradation of alkylenebis (dithiocarbamate) in soil, water, plants, and animals follows the common pathways. The disassociation of the metal complex and oxidation reactions lead to the formation of carbon disulfide (CS2), ethylene thiuram disulfide (ETD), ethylene thiuram monosulfide (ETM), and isothiocyanate as major products. Further degradation yielded ethylenethiourea (ETU), ethyleneurea (EU), and 2-imidazoline as terminal products. Persistence is the net result of many interacting factors. Chemical properties of pesticides such as volatility, solubility, stability to ultraviolet irradiation, tendency to adsorb onto or dissolve into tissue surfaces, ease of hydrolysis, sensitivity to humid atmospheres, potentiality to polymerize with or without UV irradiation, excitation, possible isomerization or other rearrangement, etc., are all important properties that play a significant role in persistence. In considering persistence, it is necessary to take into account the metabolism or alternation products of a pesticide besides the study of the residues of the parent pesticides itself.

Sewage treatment systems: Microbiological aspects

Abstract: Publisher Summary This chapter is concerned with determining the functioning of the micro-organisms in the overall efficiency and effectiveness of the treatment systems along with the analysis of the biotransformations as the basic unit of the waste treatment scenario In describing the treatment of sewage to reduce the microbial pathogenesis and biochemical oxygen demand, it is conventional to refer to the process applied in terms of the type of the treatment involved as the sewage passes through the three basic processes of sewage treatment, which includes the preliminary treatment for the removal of gross solids and grit, secondary treatment for the biooxidation and the tertiary treatment for the removal of fine solids from the effluents Experimentation on an integrated aerobic and anaerobic system for the treatment of sewage to achieve a greater COD/BOD removal is the present-day research need in the field of effluent treatment Parallel advances are being made in genetic engineering for raising the micro-organisms, capable of degrading the constituents in physiologically stressed environment, which can be used as immensely treasured biological resources along with the integrated anaerobic and aerobic system for the sewage treatment purposes

Biotransformations and biodegradation in extreme environments

Abstract: Publisher Summary This chapter discusses biotransformations and biodegradation in extreme environments. It also considers the ability of micro-organisms to at least survive in extremes of radiation exposure. This microbial capability to thrive under extreme conditions has practical implications in applied microbiology, hence providing the justification of this volume. One of its areas is the bioremediation of organic contaminants and transformation of metals, and the purpose of this chapter is to present an account of some of the researches that have been carried out in recent years. The bulk of the following discussion focuses on metal reduction, as interest in this field has been relatively more intense in recent years. Metal oxidation and metal volatilization in extreme conditions are briefly discussed. Interest in extremophiles for applied microbiology is growing, and the possible uses of these organisms for metal transformation and organic pollutant degradation is being evaluated by numerous researchers. Thermophiles are amongst the many organisms for which the whole genome sequence has been determined. There is very limited information on alkalophilic metal reduction or organic biodegradation. Thus, if there is a need for remediation at high pH sites, the need could foster research in the genomics of alkalophiles. Much work remains to be done in defining how all these organisms adapt to extreme environments.