About this Research Topic
The viability of lignocellulosic-based biorefineries depends on the successful use of all fractions of the material. Among them, integration of the hemicellulose fraction in biorefineries, especially for the production of high value compounds, is a strategy that has been strongly considered to improve the revenues, while contributing to increasing the diversity of products that can be obtained. Hemicellulose represents about one-third of the biomass composition, and is constituted by a heterogeneous group of polymers, including the pentoses xylose and arabinose, which are the main sugars present in hemicellulosic hydrolysates. The conversion of those sugars by fermentative routes has been studied for decades to obtain different compounds of interest such as ethanol, acetone, butanol, and higher value chemicals such as succinic acid, lactic acid, xylooligosaccharides, furfural, xylitol, pigments, biopolymers, among others. Although many works dealing with wild or engineered microbial strains able to metabolize pentoses have been published, there are persistent drawbacks in fermentative processes using C5-sugars as a substrate. Those drawbacks include low productivity due to the slow metabolization of pentose by microorganisms, and due to the presence of toxic compounds in pentose-rich hemicellulosic hydrolysates.
A number of strategies has been evaluated to overcome those drawbacks, including the development of methods for detoxification of hydrolysates, as well as to generate a lower amount of toxic compounds during the pretreatment step, adaptive laboratory evolution of microbial strains, and genetic engineering of strains to improve their pentose assimilation and tolerance to toxic compounds. Recent advances in this area also include efforts in nanotechnology, new molecular biology and biochemical engineering tools, and evaluation of alternative bioreactors for fermentation. Mathematical modeling and evaluation of economic, environmental, and social sustainability aspects are also of great relevance to support decisions on the integration of pentose fermentation processes in biorefineries. Therefore, the topic editors are asking for studies on new approaches and advances in pentose fermentation for integration in biorefineries, also seeking reports about pretreatment able to result in low generation of toxic compounds, detoxification methods, and adaptation of microorganisms to hemicellulosic hydrolysates.
Topics covered in this Research Topic include, but are not limited to:
• New highly efficient pentose-fermenting microbial strains
• Cell factory engineering applied to pentose fermentation
• Adaptive laboratory evolution of microbial strains for conversion of pentose-rich hemicellulosic hydrolysates
• New detoxification methods for hemicellulosic hydrolysates
• Hemicellulose pretreatment with generation of low amount of toxic compounds
• Nanotechnology applied to the use of hemicellulose in biorefineries
• Bioreactors and scale-up of processes for pentose fermentation
• Mathematical modeling related to the production and/or fermentation of pentose-rich hydrolysates
• Sustainability assessment of pentose fermentation processes and/or their integration in biorefineries
Keywords: hemicellulose, biomass pretreatment, pentose-rich hydrolysates, toxic compounds in hemicellulosic hydrolysates, molecular biology applied to pentose fermentation
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