Robert J. Seviour

Growth of Filamentous Fungi in Submerged Culture: Problems and Possible Solutions

ABSTRACT:  Filamentous fungi are important organisms industrially and continue to attract research interest as microbiologists attempt to overcome the problems associated with their behavior in submerged culture. This review critically examines the literature describing these problems and where available suggests possible solutions to them. The influence of the chemical and physical environment on culture morphology, the process engineering challenges presented by different fungal morphologies, and the relationship between fungal morphology and metabolite production are all discussed.

Microbial Ecology of Activated Sludge

Microbial Ecology of Activated Sludge, written for both microbiologists and engineers, critically reviews our current understanding of the microbiology of activated sludge, the most commonly used process for treating both domestic and industrial wastes. The contributors are all internationally recognized as leading research workers in activated sludge microbiology, and all have made valuable contributions to our present understanding of the process. The book pays particular attention to how the application of molecular methods has changed our perceptions of the identity of the filamentous bacteria causing the operational disorders of bulking and foaming, and the bacteria responsible for nitrification and denitrification and phosphorus accumulation in nutrient removal processes. Special attention is given to how it is now becoming possible to relate the composition of the community of microbes present in activated sludge, and the in situ function of individual populations there, and how such information might be used to manage and control these systems better. Detailed descriptions of some of these molecular methods are provided to allow newcomers to this field of study an opportunity to apply them in their research. Comprehensive descriptions of organisms of interest and importance are also given, together with high quality photos of activated sludge microbes. Activated sludge processes have been used globally for nearly 100 years, and yet we still know very little of how they work. In the past 15 years the advent of molecular culture independent methods of study have provided tools enabling microbiologists to understand which organisms are present in activated sludge, and critically, what they might be doing there. Microbial Ecology of Activated Sludge will be the first book available to deal comprehensively with the very exciting new information from applying these methods, and their impact on how we now view microbiologically mediated processes taking place there. As such it will be essential reading for microbial ecologists, environmental biotechnologists and engineers involved in designing and managing these plants. It will also be suitable for postgraduate students working in this field.

A simple HPLC method for analysing diaminopimelic acid diastereomers in cell walls of Gram-positive bacteria

A simple and sensitive method for separating and detecting the LL, DD and meso diastereomers of the dibasic amino acid diaminopimelic acid (DAP) in the peptidoglycan of Gram‐positive bacteria is described. This method is based on reverse phase HPLC separation of chiral derivatives of DAP followed by fluorescence detection of the o‐phthaldehyde derivatives. Its application to the analyses of cell walls of several Gram‐positive bacteria is described, where 10 mg or less of dry cells is required.

Development and use of fluorescent in situ hybridization probes for the detection and identification of Microthrix parvicella in activated sludge

Summary Four 16S rRNA directed oligonucleotide probes (MPA probes) specific for the activated sludge bulking and foaming filamentous bacterium “ Microthrix parvicella ” were designed and evaluated for the in situ detection and identification of this organism. A method for successful permeabilization of “ M. parvicella ” cells employing mutanolysin was developed. Hybridization stringency for the probes was empirically determined with activated sludge samples because “ M. parvicella ” cannot be cultured to give adequate amounts of biomass. A probe complimentary to the 16S rRNA of most bacteria (EUB338) was used to confirm the presence and accessibility of sufficient numbers of ribosomes in “ M. parvicella ”. None of a wide range of pure cultures of bacteria gave positive hybridization signals with any of the MPA probes. Three of the developed probes (MPA60, MPA223 and MPA645) were highly specific for filaments morphologically identified as “ M. parvicella ” in activated sludge samples while one probe (MPA650), required the use of two competitor probes to be highly “ M. parvicella ”-specific. None of the cells morphologically identified as “ M. parvicella ” gave positive hybridization signals with a previously reported probe for high mol%G+C gram positive bacteria. “ M. parvicella ” filaments in activated sludge plants from Australia, France and Germany bound all four MPA probes suggesting that the same genotype is present in each of these countries. A combination of in situ hybridization probing and staining with DAPI showed segments of the “ M. parvicella ” filaments that contained large amounts of polyphosphates were low in ribosomes. From this, we concluded that the storage of polyphosphates could be a survival strategy for “ M. parvicella ”.

The Microbiology of Activated Sludge

Preface. 1. Introduction to the microorganisms found in activated sludge processes R.J. Seviour, L.L. Blackall. 2. The activated sludge process R.J. Seviour, et al. 3. The normal microbial communities of activated sludge plants R.J. Seviour. 4. Factors affecting the occurrence of filamentous bacteria in activated sludge plants R.J. Seviour. 5. Current taxonomic status of filamentous bacteria found in activated sludge plants R.J. Seviour, L.L. Blackall. 6. Bulking L.L. Blackall. 7. Foaming J. Soddell. 8. The microbiology of nitrogen removal in activated sludge systems L.L. Blackall, P. Burrell. 9. Microbiological aspects of phosphorus removal in activated sludge systems P.I. Bond, G.N. Rees. 10. Practical methods for the examination and characterization of activated sludge K.C. Lindrea, et al. 11. Descriptions of the filamentous bacteria causing bulking and foaming in activated sludge plants E.M. Seviour, et al. Flossary, References. Index.

Noncellulolytic fungal β-glucanases: Their physiology and regulation

The occurrence, regulation, and action of fungal enzymes capable of degrading noncellulosic β-glucans, especially 1,3-β- and 1,6-β-glucans, are reviewed. Special consideration is given to their roles in both metabolic and morphogenetic events in the fungal cell, including cell wall extension, hyphal branching, sporulation, budding, and autolysis. Also examined are the protocols currently available for their purification, with some of the properties of purified β-glucanases discussed in terms of their potential applications in industrial, agricultural, and medical fields.

Identity and ecophysiology of filamentous bacteria in activated sludge.

Excessive growth of filamentous bacteria in activated sludge wastewater treatment plants (WWTPs) can cause serious operational problems. With some filaments there may be the problem of bulking, where inadequate flocculation and settling of the biomass in the secondary clarifier results in a carryover of solids with the final treated liquid effluent. Their proliferation often encourages the development of stable foams on the surface of the reactors, and these foams may impact negatively on plant performance and operation. The availability of culture-independent molecular methods now allows us to identify many of the more common filamentous organisms encountered in WWTPs, which are phylogenetically diverse, affiliating to seven separate bacterial phyla. Furthermore, the extensive data published in the past decade on their in situ behaviour from the application of these culture-independent methods have not been summarized or reviewed critically. Hence, here, we attempt to discuss what we now know about their identity, ecophysiology and ecological niches and its practical value in better managing activated sludge processes. Some of this knowledge is already being applied to control and manage full-scale WWTPs better, and the hope is that this review will contribute towards further developments in this field of environmental microbiology.

Production of Pullulan and other Exopolysaccharides by Filamentous Fungi

AbstractA great deal of recent interest has been shown in the ability of some microbes to synthesize exopolysaccharides. Most attention has been directed toward the prokaryote producers, yet many filamentous fungi also produce exopolysaccharides that have chemical and physical properties of considerable commercial potential. Surprisingly little is known about how and why fungi overproduce these metabolites and how yields are affected by both the physical and chemical environments. This review attempts to critically appraise the current literature on fungal exopolysaccharides, considers their chemical diversity, and examines factors that seem to affect their production. Although much of the published work has been carried out with the α-glucan pullulan, there is considerable literature on the β-glucans and, hence, both of these are discussed.

Does the agitation rate and/or oxygen saturation influence exopolysaccharide production by Aureobasidium pullulans in batch culture?

Abstract  When Aureobasidium pullulans was grown at a number of agitation rates under batch conditions, exopolysaccharide yields were dramatically reduced at high rates i.e. at least 750 rpm. Investigations with gas blending, which allowed pO2 manipulation and control independently of the agitation rate, showed that this yield reduction was due solely to the high pO2 levels that occurred at these agitation rates. Thus, polysaccharide production at 1000 rpm could be elevated by maintaining the pO2 at a low level during the initial phase of the fermentation. However, both the timing of the pO2 decrease and the level at which it was maintained were crucial for obtaining yields at 1000 rpm, similar to those observed at low agitation rates.

Ecology of the Microbial Community Removing Phosphate from Wastewater under Continuously Aerobic Conditions in a Sequencing Batch Reactor

ABSTRACT All activated sludge systems for removing phosphate microbiologically are configured so the biomass is cycled continuously through alternating anaerobic and aerobic zones. This paper describes a novel aerobic process capable of decreasing the amount of phosphate from 10 to 12 mg P liter−1 to less than 0.1 mg P liter−1 (when expressed as phosphorus) over an extended period from two wastewaters with low chemical oxygen demand. One wastewater was synthetic, and the other was a clarified effluent from a conventional activated sludge system. Unlike anaerobic/aerobic enhanced biological phosphate removal (EBPR) processes where the organic substrates and the phosphate are supplied simultaneously to the biomass under anaerobic conditions, in this aerobic process, the addition of acetate, which begins the feed stage, is temporally separated from the addition of phosphate, which begins the famine stage. Conditions for establishing this process in a sequencing batch reactor are detailed, together with a description of the changes in poly-β-hydroxyalkanoate (PHA) and poly(P) levels in the biomass occurring under the feed and famine regimes, which closely resemble those reported in anaerobic/aerobic EBPR processes. Profiles obtained with denaturing gradient gel electrophoresis were very similar for communities fed both wastewaters, and once established, these communities remained stable over prolonged periods of time. 16S rRNA-based clone libraries generated from the two communities were also very similar. Fluorescence in situ hybridization (FISH)/microautoradiography and histochemical staining revealed that “Candidatus Accumulibacter phosphatis” bacteria were the dominant poly(P)-accumulating organisms (PAO) in both communities, with the phenotype expected for PAO. FISH also identified large numbers of betaproteobacterial Dechloromonas and alphaproteobacterial tetrad-forming organisms related to Defluviicoccus in both communities, but while these organisms assimilated acetate and contained intracellular PHA during the feed stages, they never accumulated poly(P) during the cycles, consistent with the phenotype of glycogen-accumulating organisms.