Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA.
Division of Crop Improvement, ICAR Sugarcane Breeding Institute, Coimbatore, India.
Biotechnol Bioeng. 2021 Mar;118(3):1066-1090. doi: 10.1002/bit.27639. Epub 2020 Dec 16.
Lignocellulosic biofuels and chemicals have great potential to reduce our dependence on fossil fuels and mitigate air pollution by cutting down on greenhouse gas emissions. Chemical, thermal, and enzymatic processes are used to release the sugars from the lignocellulosic biomass for conversion to biofuels. These processes often operate at extreme pH conditions, high salt concentrations, and/or high temperature. These harsh treatments add to the cost of the biofuels, as most known biocatalysts do not operate under these conditions. To increase the economic feasibility of biofuel production, microorganisms that thrive in extreme conditions are considered as ideal resources to generate biofuels and value-added products. Halophilic archaea (haloarchaea) are isolated from hypersaline ecosystems with high salt concentrations approaching saturation (1.5-5 M salt concentration) including environments with extremes in pH and/or temperature. The unique traits of haloarchaea and their enzymes that enable them to sustain catalytic activity in these environments make them attractive resources for use in bioconversion processes that must occur across a wide range of industrial conditions. Biocatalysts (enzymes) derived from haloarchaea occupy a unique niche in organic solvent, salt-based, and detergent industries. This review focuses on the use of haloarchaea and their enzymes to develop and improve biofuel production. The review also highlights how haloarchaea produce value-added products, such as antibiotics, carotenoids, and bioplastic precursors, and can do so using feedstocks considered "too salty" for most microbial processes including wastes from the olive-mill, shell fish, and biodiesel industries.
木质纤维素生物燃料和化学品具有很大的潜力，可以减少我们对化石燃料的依赖，并通过减少温室气体排放来减轻空气污染。化学、热和酶处理用于从木质纤维素生物质中释放糖，以将其转化为生物燃料。这些过程通常在极端的 pH 值条件、高盐浓度和/或高温下运行。这些苛刻的处理增加了生物燃料的成本，因为大多数已知的生物催化剂在这些条件下无法运行。为了提高生物燃料生产的经济可行性，被认为在极端条件下茁壮成长的微生物被视为生产生物燃料和增值产品的理想资源。嗜盐古菌（haloarchaea）是从高盐浓度接近饱和（1.5-5 M 盐浓度）的高盐度超盐环境中分离出来的，包括 pH 和/或温度极端的环境。嗜盐古菌及其酶的独特特性使它们能够在这些环境中维持催化活性，这使它们成为在必须在广泛的工业条件下进行的生物转化过程中使用的有吸引力的资源。来源于嗜盐古菌的生物催化剂（酶）在有机溶剂、盐基和洗涤剂工业中占据独特的地位。本综述重点介绍了嗜盐古菌及其酶在生物燃料生产中的开发和改进中的应用。综述还强调了嗜盐古菌如何生产增值产品，如抗生素、类胡萝卜素和生物塑料前体，并且可以使用被认为对大多数微生物过程“太咸”的原料来生产，包括橄榄厂、贝类和生物柴油行业的废物。
