Pretreatment of Lignocellulosic Biomass Using Microorganisms: Approaches, Advantages, and Limitations

Abstract

Additional information is available at the end of the chapter http://dx.doi.org/10.5772/55088 . IntroductionMuch of Earth s recent geologic history is dominated by periods of extensive glaciation, with relatively low global mean temperatures and correspondingly low atmospheric CO concentrations [ ]. The current interglacial period stands out as an anomaly because the atmospheric CO concentration has risen sharply above the range of approximately -parts per million by volume that has defined the past , years to reach levels that are nearly % higher than the biosphere has experienced over this time frame [ ]. This rapid increase in CO concentration is primarily due to the release of ancient fixed atmospheric CO into the modern atmosphere through the combustion of fossil fuel resources over the past years. Since it is clear from ice core records that atmospheric CO concentration has a strong positive correlation to global temperature, it is expected that changes to global climate are forthcoming [ ]. There are substantial uncertainties regarding the ability of terrestrial and oceanic carbon sinks to absorb this anthropogenic CO on time scales that are relevant to human society [ ], so the continued release of ancient CO into the modern atmosphere at current rates carries with it an important risk of inducing climate changes of unknown amplitude along with a host of ancillary changes that are difficult to predict with certainty. This has led to the search for alternatives to fossil fuels to meet a rising global energy demand, and one such option is the use of extant organic matter to produce energy. This resource contains carbon that was fixed from the modern atmosphere, which means it does not result in a net increase in atmospheric CO upon combustion.

An Overview of Lignocellulose and Its Biotechnological Importance in High-Value Product Production

“…Most of these fungi are Ascomycetes, Deuteromycetes, or Basidiomycetes; they live on wood and degrade the wood components, thereby causing wood rots [71,72]. Brown rot fungi, for instance, constitute around 6-10% of wood decay fungi, and they not only degrade cellulose and hemicellulose but also modify lignin through a demethylation reaction [72][73][74]. It was reported that lignocellulose degradation occurs in the S2 layer of the cell wall via oxidation and hydrolysis mechanisms [75].…”

“…It was reported that lignocellulose degradation occurs in the S2 layer of the cell wall via oxidation and hydrolysis mechanisms [75]. White rots are the most effective fungi in degrading the main components of the cell wall (e.g., lignin, hemicellulose, and cellulose) [72][73][74].…”

Literature Review on Pretreatments of Lignocellulosic Biomass

“…[22]. The pretreatment step is regarded as a crucial and costly unit process in converting lignocellulosic materials into fuels, and it is the major contributor to the costs of producing energy from biomass [23,24]. In contrast to physicochemical methods, biological pretreatment of lignocellulosic biomass is a safe, environmentally friendly, less energy intensive and cheap alternative [2,25].…”

Comparative Study on Quality of Fuel Pellets from Switchgrass Treated with Different White-Rot Fungi

“…Biological pretreatment, in contrast to the thermochemical and physicochemical pretreatment methods, is an energy-saving and environmentally benign process, which breaks down the lignocellulosic matrix using microorganisms (fungi or bacteria) under liquid-state or solid-state fermentation (SSF) [20,21]. Fungi, including white-, brown-, and soft-rot fungi, possess highly efficient enzymatic systems that are responsible for the degradation of lignocellulosic materials.…”