Search

Appropriate bioprocessing of lignocellulosic materials into ethanol could address the world’s insatiable appetite for energy while mitigating greenhouse gases. Bioethanol is an ideal gasoline extender and is widely used in many countries in blended form with gasoline at specific ratios to improve fuel characteristics and engine performance. Although the bioethanol production industry has long been operational, finding a suitable microbial agent for the efficient conversion of lignocelluloses is still an active field of study. Among available microbial candidates, engineered bacteria may be promising ethanol producers while may show other desired traits such as thermophilic nature and high ethanol tolerance. This review provides the current knowledge on the introduction, overexpression, and deletion of the genes that have been performed in bacterial hosts to achieve higher ethanol yield, production rate and titer, and tolerance. The constraints and possible solutions and economic feasibility of the processes utilizing such engineered strains are also discussed.

Human gut microbiota contains a large, complex, dynamic microbial community of approximately 1014 microbes from more than 1,000 microbial species, i.e., equivalent to 4 × 106 genes. Numerous evidence links gut microbiota with human health and diseases. Importantly, gut microbiota is involved in the development and function of the brain through a bidirectional pathway termed as the gut-brain axis. Interaction between gut microbiota and immune responses can modulate the development of neuroinflammation and cancer diseases in the brain. With respect of brain cancer, gut microbiota could modify the levels of antioxidants, amyloid protein and lipopolysaccharides, arginase 1, arginine, cytochrome C, granulocyte–macrophage colony-stimulating factor signaling (GM-CSF), IL-4, IL-6, IL-13, IL-17A, interferon gamma (IFN-γ), reactive oxygen species (ROS), reactive nitrogen species (e.g., nitric oxide and peroxynitrite), short-chain fatty acids (SCFAs), tryptophan, and tumor necrosis factor-β (TGF-β). Through these modifications, gut microbiota can modulate apoptosis, the aryl hydrocarbon receptor (AhR), autophagy, caspases activation, DNA integrity, microglia dysbiosis, mitochondria permeability, T-cell proliferation and functions, the signal transducer and activator of transcription (STAT) pathways, and tumor cell proliferation and metastasis. The outcome of such interventions could be either oncolytic or oncogenic. This review scrutinizes the oncogenic and oncolytic effects of gut microbiota by classifying the modification mechanisms into (i) amino acid deprivation (arginine and tryptophan); (ii) kynurenine pathway; (iii) microglia dysbiosis; and (iv) myeloid-derived suppressor cells (MDSCs). By delineating the complexity of the gut-microbiota-brain-cancer axis, this review aims to help the research on the development of novel therapeutic strategies that may aid the efficient eradication of brain cancers.

Background The accumulation of extracellular plaques containing amyloid-β protein (Aβ) in the brain is one of the main pathological hallmarks of Alzheimer's disease (AD). Aβ peptide can promote the production of highly volatile free radicals and reactive oxygen species (ROS) that can induce oxidative damage to neurons and astrocytes. At present, numerous studies have investigated the neuroprotective and glioprotective effects of natural products derived from plants, animals, and microorganisms. Objective We investigated the glioprotective effect of secondary metabolites obtained from Herpetosiphon sp. HM 1988 against Aβ40-induced toxicity in human primary astrocytes. Methods The protective effect of bacterial secondary metabolites against Aβ40-induced inducible nitric oxide synthase (iNOS) activity was evaluated using the citrulline assay. To confirm the iNOS activity, nitrite production was assessed using the fluorometric Griess diazotization assay. Intracellular NAD+ depletion and lactate dehydrogenase (LDH) release in human primary astrocytes were also examined using well-established spectrophotometric assays. Results Our results indicate that Aβ40 can induce elevation in iNOS and LDH activities, nitrite production, and cellular energy depletion. Importantly, extract of Herpetosiphon sp. HM 1988 decreased iNOS activity, nitrite production, and LDH release. In addition, metabolites of the strain were able to restore cellular energy deficits through inhibition of NAD+ depletion mediated by Aβ40. Conclusion These findings suggest that Herpetosiphon metabolites may represent a promising, novel source for the prevention of Aβ toxicity in AD.

Currently, the modern world is facing with a major challenge regarding the production of renewable energy for phasing out fossil fuels. Lignocellulosic biomass can potentially be used as a substrate for the production of a diverse range of different biofuels such as bioethanol while not triggering food vs. fuel debate. Generally, the bioethanol production from lignocellulosic biomass involves four major steps including lignocellulose delignification/pretreatment, hydrolysis (i.e., chemical or enzymatic), hydrolyzate sugar fermentation, and distillation. The economic and environmental feasibilities of the mentioned process could significantly be enhanced through the application of phytopathogenic fungi or their enzyme cocktails. Typically, necrotrophic pathogenic fungi have exceptionally high capabilities for a copious production of various hydrolytic enzymes with activity on wide range of plant biomass, compared to biotrophic or hemibiotrophic ones. In this chapter, ten filamentous plant-pathogenic fungi species belonging to six genera, including Fusarium, Aspergillus, Phoma, Cryphonectria, Ustilago, and Colletotrichum, have comprehensively been discussed in respect to hydrolytic enzyme capabilities from bioethanol industry viewpoint. On this basis, their potential for application in simultaneous saccharification and fermentation (or co-fermentation), separate hydrolysis and fermentation, and consolidated bioprocessing process has been investigated. Eventually, their genome richness in respect to the construction of lignocellulose-degrading microorganisms or ethanologens with astonishing hydrolysis production ability from these fungi has also been scrutinized.

Among many alternatives, biodiesel is considered as one of the most promising biofuels for phasing out fossil-derived fuels and mitigating their adverse ecological impacts. However, conventional alkali- or acid-catalyzed transesterification of plant oils triggers food security, economic, and even environmental (e.g., land-use change and greenhouse gas emissions) challenges. In contrast, advanced biodiesel (i.e., second-generation biodiesel) could be synthesized from oleaginous microorganisms such as fungal and yeast. The most oleaginous fungal genera are Alternaria, Aspergillus, Chaetomium, Colletotrichum, Cunninghamella, Epicoccum, Mortierella, Mucor, Thamnidium, and Zygorhynchus. On the other hand, Yarrowia, Candida, Rhodotorula, Rhodosporidium, Aureobasidium, Cryptococcus, Metschnikowia, Kodamaea, Trichosporon, Sporidiobolus, Sporobolomyces, Occultifur, Starmerella, Pichia, and Lipomyces are the most common oleaginous yeast genera. Typically, the main lipid classes produced by oleaginous fungi and yeasts are polyunsaturated fatty acids (PUFAs, such as arachidonic acid, c-linolenic acid, dihomo-γ-linolenic acid, docosahexaenoic acid, and eicosapentanoic acid) and triglycerides (TGs) and sterol esters (SEs), respectively. Alternatively, oleaginous yeast or fungal-origin lipases could be exploited in biodiesel production via enzymatic transesterification approach. It is worth mentioning that the most widely used lipases in biodiesel industry are those extracted from yeasts (e.g., Candida antarctica and Candida rugosa) and filamentous fungi (e.g., Aspergillus niger, Penicillium expansum, Rhizomucor miehei, Rhizopus oryzae, and Thermomyces lanuginosus). In this chapter, the current status for the application of different single-cell oil (SCO)-producing filamentous fungi and yeast species is scrutinized in the first part. Same section also deals with some technological strategies for reducing SCO production cost with a particular attention on the abilities of these microorganisms for assimilating different organic wastes. In the second part of the chapter, yeast and fungal lipases as biocatalyst for biodiesel production are discussed. Overall, despite some improvements, further research in this field with respect to identification of novel oleaginous microorganisms (with high lipase and/or lipid content) as well as development of more efficient technologies (microbial fermentation, oil extraction, and biodiesel production) must be conducted to address some techno-economic constraints of SCO-based biodiesel industry.

Fossil fuels and chemical pesticides could probably be blamed for future human downfall. Therefore, the global dependence on fossil fuels must be reduced immediately due to climate change, environmental issues, and health complications. The latter two negative effects could also be rendered by chemical pesticides. Among renewable energy alternatives, liquid biofuels have higher compatibility with the current fuel infrastructures and engines (i.e., transportation, storage, and engine systems), and hence, are very promising for transportation sector. Bioethanol, a liquid biofuel, is an ideal gasoline extender and is widely used in many countries in blended form with gasoline at specific ratios to improve fuel characteristics and engine performance. Although the bioethanol production industry has long been operational, finding suitable and sustainable feedstock is still an active field of study. The consumption of food/feed commodities such as sugarcane and corn (i.e., the first-generation bioethanol) has raised food vs. fuel debate. Alternatively, scientists have concentrated on the second-generation bioethanol, which consumes wastes such as lignocelluloses. However, huge amounts of hydrolytic enzymes, particularly cellulases, are required that contribute to high bioethanol production cost. Fungal biocontrol agents are superb producers of these enzymes, while at the same time they could be used as effective biological pesticides for sustainable agriculture. In this chapter, a novel viewpoint is put forward for sustainable direct production of bioethanol from lignocellulose by fungi, which could easily be separated at the end of the process and be exploited as biological control agents. For this purpose, several promising species within Fusarium, Paecilomyces, Pichia, and Trichoderma along with two species including Aspergillus oryzae and Pochonia chlamydosporia are comprehensively evaluated and scrutinized. The characteristics of these fungi could be further improved and harnessed for a dual production of biocontrol agents and bioethanol, improving the economic and environmental feasibilities of lignocellulose-based bioethanol production.

The appropriate processing of various plant biomass residues into biofuels could address the world’s insatiable appetite for energy. To achieve such a goal, an efficient and ecofriendly pretreatment method to break the lignocellulosic materials into fermentable sugars is pivotal. Among various candidate methods, anaerobic gut fungi could provide economic and efficient hydrolytic enzymes for biological pretreatment of lignocellulosic constituents (excluding lignin). The present chapter provides an insight into the taxonomy, life cycle, cultivation, isolation, and preservation of Neocallimastigomycota. Thereafter, the interaction between these fungi and other microorganisms in their natural ecosystem (i.e., rumen) is reviewed while discussing anaerobic gut fungal hydrolytic enzymes (recombinant enzymes included) for biomass degradation. Then, the main focus is placed on the potential application of this phylum of fungi for biofuel (ethanol and biogas) production. Overall, the efficiency of Neocallimastigomycota for biological pretreatment of plant biomass for bioethanol or biogas production has been overlooked. Anaerobic nature (compatible with ethanol and anaerobic digestion process), high enzyme production capabilities, fast and easy cultivation, and ecofriendly nature are some of the advantages of these fungi that could be exploited for higher economic profitability of the biofuel industry.

There are 17 human-biting ticks known in Australia. The bites of Ixodes holocyclus, Ornithodoros capensis, and Ornithodoros gurneyi can cause paralysis, inflammation, and severe local and systemic reactions in humans, respectively. Six ticks, including Amblyomma triguttatum, Bothriocroton hydrosauri, Haemaphysalis novaeguineae, Ixodes cornuatus, Ixodes holocyclus, and Ixodes tasmani may transmit Coxiella burnetii, Rickettsia australis, Rickettsia honei, or Rickettsia honei subsp. marmionii. These bacterial pathogens cause Q fever, Queensland tick typhus (QTT), Flinders Island spotted fever (FISF), and Australian spotted fever (ASF). It is also believed that babesiosis can be transmitted by ticks to humans in Australia. In addition, Argas robertsi, Haemaphysalis bancrofti, Haemaphysalis longicornis, Ixodes hirsti, Rhipicephalus australis, and Rhipicephalus sanguineus ticks may play active roles in transmission of other pathogens that already exist or could potentially be introduced into Australia. These pathogens include Anaplasma spp., Bartonella spp., Burkholderia spp., Francisella spp., Dera Ghazi Khan virus (DGKV), tick-borne encephalitis virus (TBEV), Lake Clarendon virus (LCV), Saumarez Reef virus (SREV), Upolu virus (UPOV), or Vinegar Hill virus (VINHV). It is important to regularly update clinicians' knowledge about tick-borne infections because these bacteria and arboviruses are pathogens of humans that may cause fatal illness. An increase in the incidence of tick-borne infections of human may be observed in the future due to changes in demography, climate change, and increase in travel and shipments and even migratory patterns of birds or other animals. Moreover, the geographical conditions of Australia are favorable for many exotic ticks, which may become endemic to Australia given an opportunity. There are some human pathogens, such as Rickettsia conorii and Rickettsia rickettsii that are not currently present in Australia, but can be transmitted by some human-biting ticks found in Australia, such as Rhipicephalus sanguineus, if they enter and establish in this country. Despite these threats, our knowledge of Australian ticks and tick-borne diseases is in its infancy.

Advancement of science has gifted the human a longer life; however, as neuron cells do not regenerate, the number of people with neurodegeneration disorders rises with population aging. Neurodegeneration diseases occur as a result of neuronal cells loss caused by environmental factors, genetic mutations, proteopathies and other cellular dysfunctions. The negative direct or indirect contributions of various microorganisms in onset or severity of some neurodegeneration disorders and interaction between human immune system and pathogenic microorganisms has been portrayed in this review article. This association may explain the early onset of neurodegeneration disorders in some individuals, which can be traced through detailed study of health background of these individuals for infection with any microbial disease with neuropathogenic microorganisms (bacteria, fungi, viruses). A better understanding and recognition of the relation between microorganisms and neurodegeneration disorders may help researchers in development of novel remedies to avoid, postpone, or make neurodegeneration disorders less severe.

More than other bacteria Actinobacteria, especially the mycelium forming ones impress by their appearance, the color of the aerial mycelium, of the substrate mycelium and also of pigments that diffuse into the agar (Cross 1989; Krasil’nikov 1979; Kuster 1976) and the morphology of their differentiation stages (Gottlieb 1961) which will be described in the later chapters. The aerial mycelium which makes them look like a fungus and the often three dimensional shape of the colony. The color of the aerial mycelium has been used by many groups for a first classification (Flaig and Kutzner 1960; Ettlinger et al. 1958; Shirling and Gottlieb 1966; Tresner and Backus 1963). The main classification groups are: white, grey white, cream (Streptomyces albus); yellow-grey (Streptomyces griseus); rose, pale violet (Streptomyces fradiae, Microbispora rosea), rose-grey (Streptomyces lavendulae); pale brown, red brown (Streptomyces fragilis); pale blue, grey-blue (Streptomyces viridochromogenes); blue green (Streptomyces glaucescens, Actinomadura rubrobrunnea); pale green, green (Streptomyces prasinus, Microtetraspora viridis); pale grey, grey (Streptomyces violaceoruber, Microtetraspora glauca) (Blinov and Khokhlov 1970). By the description of the aerial mycelium color three points have to be kept in mind. The first is that the typical color is only expressed if the culture is also sporulating. Different species often sporulate on different media, so a number of agar cultures have to be prepared to get good results. The second is the diffusion of pigments from the substrate mycelium into the aerial mycelium which can have influences on the shade of the aerial mycelium. The third is the experience with many different Actinobacteria and their pigmentation, to do this grouping well. It is therefore very important to use the same media and culture conditions for all strains that will be compared. Over the years the use of the media from Shirling and Gottlieb (1966) from the “International Streptomyces Project/ISP” has been established in nearly all labs working with Actinobacteria (composition of media, see Sect. 11.2.1).

The kynurenine pathway is important in cellular energy generation and limiting cellular ageing as it degrades about 90% of dietary tryptophan into the essential co-factor NAD+ (nicotinamide adenine dinucleotide). Prior to the production of NAD+, various intermediate compounds with neuroactivity (kynurenic acid, quinolinic acid) or antioxidant activity (3-hydroxykynurenine, picolinic acid) are synthesized. The kynurenine metabolites can participate in numerous neurodegenerative disorders (Alzheimer disease, amyotrophic lateral sclerosis, Huntington disease, and Parkinson disease) or other diseases such as AIDS, cancer, cardiovascular diseases, inflammation, and irritable bowel syndrome. Recently, the role of gut in affecting the emotional and cognitive centres of the brain has attracted a great deal of attention. In this review, we focus on the bidirectional communication between the gut and the brain, known as the gut-brain axis. The interaction of components of this axis, namely, the gut, its microbiota, and gut pathogens; tryptophan; the kynurenine pathway on tryptophan availability; the regulation of kynurenine metabolite concentration; and diversity and population of gut microbiota, has been considered.

Microbial-derived products, while do not have many environmental side effects of their synthetic counterparts, have proved more efficient than those synthetically obtained. The nature has provided a treasure of microorganisms with capabilities to produce vast variety of novel compounds. This ability has been arised during long last of evolution and adaptation to diverse chemical and physical microenviroments. Microbial-derived metabolites have made their own space in industries and therefore human life. Among these microorganisms, halophilic and halotolerant actinobacteria are recently gaining much attentions. Metabolites and biological functions from halophilic or halotolerant members of this phylum of bacteria may resolving the ever-increasing thirst of industry for metabolites with salt-tolerancy to cope a range of issues from environmental pollution to diseases and world’s hunger. In the current chapter, it has been tried to introduce the less dealt group of halophilic and halotolerant actinobacteria, and shed light on their potential to be exploited in various industry sectors.