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Biological Agents
Published in Katarzyna Majchrzycka, Małgorzata Okrasa, Justyna Szulc, Respiratory Protection Against Hazardous Biological Agents, 2020
Neutrophils are microorganisms with an optimal pH for growth close to neutral (6–7.5) and they constitute the majority of known bacteria. Acidophilic microorganisms are organisms that are capable of functioning in an environment with a pH of < 4. They are characteristic of extreme environments such as iron and sulphur deposits, mine waters and volcanic soil. Lactic and acetic acid bacteria, numerous species of yeasts and moulds, and algae are classified as acidophiles. Alkaliphiles are microorganisms with an optimal pH for growth in the range of 8–11. This group includes many species of bacteria, including pathogenic Vibrio cholerae or Streptococcus pneumoniae, archaea and cyanobacteria. Among alkaliphiles, a group of microorganisms can be distinguished, which, apart from high pH, also requires high concentrations of sodium chloride, NaCl, for optimal growth. Such microorganisms are referred to as haloalkaliphiles and occur in extremely alkaline and saline environments such as salt lakes, salines and geothermal springs. These include sulphur oxidising bacteria and nitrifying bacteria [Duckworth 1996; Libudzisz 2019].
Microbial Electrochemical Technology Drives Metal Recovery
Published in Sonia M. Tiquia-Arashiro, Deepak Pant, Microbial Electrochemical Technologies, 2020
Xochitl Dominguez-Benetton, Jeet Chandrakant Varia, Guillermo Pozo
A long trajectory exists on how microbes associate with metals in both natural and man-made environments (Gadd 2010). The role of microbes in the binding and mineralization of metal ions (Konhauser et al. 2008; Beveridge and Murray 1976), the interactions between microbes and a variety of metals as well as metal accumulation (White et al. 1995) and the role of microbes in the generation of acidic, metal-rich mine waters (Johnson and Hallberg 2003) have been reviewed extensively. For instance, acidophiles accelerate the dissolution of pyrite and other sulfide minerals causing substantial environmental damage due to the release of acid mine drainage (AMD) into the environment. The principles governing the generation of AMD are relatively well understood. A schematic overview of the generation of AMD is presented in Figure 1.
Extremophilic Microbes and their Extremozymes for Industry and Allied Sectors
Published in Ajar Nath Yadav, Ali Asghar Rastegari, Neelam Yadav, Microbiomes of Extreme Environments, 2021
Hiran Kanti Santra, Debdulal Banerjee
Abe and Horikoshi reported that α-amylase from a piezophilic source acts on maltooligosaccharides and produces trisaccharides, tetrasaccharides at great pressure and small amount of energy (Abe and Horikoshi 2001). This particular reaction is of high importance in the food industry (Cannio et al. 2004; Giuliano et al. 2004). Other than this piezophilic proteins are of great use in the detergent and food industries (Cavicchioli et al. 2011). Acidophiles are micro-organisms that grow at optimum pH of below 3–4 (Jaenicke 1981). Endoß-glucanase from Sulfolobus solfataricus demonstrated higher stability at optimum pH of 1.8 (Huang et al. 2005). Pikuta et al. demonstrated that carboxylesterase in Ferroplasma acidiphilum has a pH optimum of approximately 2 (Pikuta et al. 2007). Enzymes produced by acidophiles have great potential for biotechnological and industrial applications for the production of biofuel and ethanol. Halophilic microbes are able to survive in excessive salt concentrations (minimum 1 M NaCl) and the establishment of different chemical, structural, physiological modifications have allowed the selectivity as well as stability of proteins with their unique physicochemical properties (Delgado-García et al. 2012; Jackson et al. 2001). Halophiles are subdivided in three groups; extreme halophiles—capable of growing at 2,500–5,200 mM NaCl, moderate halophiles—survives at 500–2,500 mM NaCl concentrations and the slightly halophilic one-grows at 200–500 mM NaCl. Halophilic extremozymes are able to survive at low water activity and in the presence of organic solvents (Datta et al. 2010; Madern et al. 1995).
Engineered Alcaligenes sp. by chemical mutagen produces thermostable and acido-alkalophilic endo-1,4-β-mannanases for improved industrial biocatalyst
Published in Preparative Biochemistry & Biotechnology, 2023
Oladipo Oladiti Olaniyi, Ademola Sunday Ajulo, Olusola Tosin Lawal, Victoria Kehinde Olatunji
Alcaligene sp. was the first bacterium to have produced β-mannanase and biocatalytically characterized from the rumen of a ruminant. Interestingly, the purified β-mannanase from the mutant had optimum activity of 50 °C compared to its wild type which was 40 °C. The engineered type also exhibited more thermo-stability compared to the wild-type and maintained very high residual activities even at extreme temperatures, a character which apparently constitutes an exception. The enzymes from the wild type and its mutant were observed to be acidophilic (acid tolerant) as they demonstrated optimal activities at pH 6.0 with exceptional relative activities at acidic and alkaline regions. The high affinity of the enzymes toward LBG as indicated by low Km values suggests high product formation with greater hydrolytic efficiency. Therefore, these enzymes could be useful for many industrial processes due to their thermostability and acido-alkalophilic nature, where extreme operational conditions are required.
Biotechnological Avenues in Mineral Processing: Fundamentals, Applications and Advances in Bioleaching and Bio-beneficiation
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Srabani Mishra, Sandeep Panda, Ata Akcil, Seydou Dembele
It has been defined in general consensus that acidophiles are the microorganisms that can live in low pH environment. Specifically, they can be classified as “moderate acidophile” having an optimal pH range of 3–5 or “extreme acidophile” which can support a pH less than 3 (Shiers, Collinson and Watling 2016). In bioleaching studies, the mostly used/preferred acidophilic microorganism belongs to the extreme acidophiles group. These microorganisms are constituted of a variety of genus, e.g., Acidithiobacillus, Sulfolobus, Acidianus and Leptospirillum (Das, Ayyappan and Chaudhury 1999). A list of potential acidophilic microorganisms reported in bioleaching along with their characteristic features can be found elsewhere (Panda et al. 2015a; Schippers 2007; Schippers et al. 2014; Valdes et al. 2010). As bioleaching environment/condition determines the growth of microorganism; acidophilic microorganisms have been classified as mesophiles, moderate thermophiles and extreme thermophiles according to their ability to support a range of temperature.