In nature, cellulose, lignocellulose and lignin are major sources of plant biomass; therefore, their recycling is indispensable for the carbon cycle. Each polymer is degraded by a variety of microorganisms which produce a battery of enzymes that work synergically. In the near future, processes that use lignocellulolytic enzymes or are based on microorganisms could lead to new, environmentally friendly technologies. This study reviews recent advances in the various biological treatments that can turn these three lignicellulose biopolymers into alternative fuels. In addition, biotechnological innovations based on natural delignification and applied to pulp and paper manufacture are also outlined.

Biodegradation and biological treatments of cellulose, hemicellulose and lignin: an overview

This review is written from the perspective of scientists working in lignocellulose bioconversion in a developing country and the aim of this review is to remind ourselves and other scientists working in related areas of lignocellulose research of the enormous economic potential of the bioprocessing of residual plant materials generally regarded as “waste”, and secondly to highlight some of the modern approaches which potentially could be used to tackle one of the major impediments, namely high enzyme cost, to speed-up the extensive commercialisation of the lignocellulose bioprocessing. Key words : lignocellulose, bioconversion, enzyme cost. 
African Journal of Biotechnology Vol. 2 (12), pp. 602-619, December 2003

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Lignocellulose biotechnology: issues of bioconversion and enzyme production

Lignocelluloses are the building blocks of allplants and are ubiquitous to most regions ofour planet. Their chemical properties make it asubstrate of enormous biotechnological value.The basic chemistry of cellulose,hemicellulose, and lignin has a profound effecton lignocellulose tertiary architecture. Theseintricate associations constitute physical andchemical barriers to lignocellulose utilizationand biodegradation in natural and man-madeenvironments. Overcoming these barriers is thekey to unlocking the commercial potential oflignocellulose. Understanding lignocellulosedegradation under natural conditions forms thebasis of any lignocellulose-based application.A variety of microorganisms and mechanisms areinvolved in the complete biodegradation oflignocellulose in natural environments rangingfrom soil and rumen ecosystems to the termitehindgut. The primary objective oflignocellulose pretreatment by the variousindustries is to access the potential of thecellulose and hemicellulose encrusted by ligninwithin the lignocellulose matrix. Currentworking technologies based on the principles ofsolid-state fermentation (SSF) are brieflyreviewed. The use of unsterile lignocellulosicsfor bioremediation purposes holds promise forcost-effective environmental clean-upendeavors. Novel lignocellulose-basedapplications have found functionality intextile, biological control, and medicalresearch fields and might be exploited there inthe near future. Ultimately, lignocellulosewill probably accompany man to his voyages intospace for interest in this field isintensifying. Therefore, proper management oflignocellulose biodegradation and utilizationcan serve to improve the quality of theenvironment, further man's understanding of theuniverse, and ultimately change local economiesand communities.

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Lignocellulose biodegradation: Fundamentals and applications

This paper provides a critical review of the literature on heat-exchanger network synthesis, the most commonly studied problem in process synthesis. After a review of solution methods, we present the chronological milestones in the development of the field and we discuss separately each of 461 related works leading up to the turn of the century. Then, we present several classification schemes of this body of work based on a number of modeling and algorithmic criteria. Finally, we offer a critical assessment of the current status of research in this area and provide suggestions for future research.

A Critical Review and Annotated Bibliography for Heat Exchanger Network Synthesis in the 20th Century

Fungal pretreatment of lignocellulosic biomass

Optimization of process plant layout with pipe routing

Mechanical pulping process is electrical energy intensive and results in low paper strength. Biomechanical pulping, defined as the fungal treatment of lignocellulosic materials prior to mechanical pulping, has shown at least 30% savings in electrical energy consumption, and significant improvements in paper strength properties compared to the control at a laboratory scale. In an effort to scale-up biomechanical pulping to an industrial level, 50 tons of spruce wood chips were inoculated with the best biopulping fungus in a continuous operation and stored in the form of an outdoor chip pile for 2 weeks. The pile was ventilated with conditioned air to maintain the optimum growth temperature and moisture throughout the pile. The control and fungus-treated chips were refined through a thermomechanical pulp mill (TMP) producing lightweight coated paper. The fungal pretreatment saved 33% electrical energy and improved paper strength properties significantly compared to the control. Since biofibers were stronger than the conventional TMP fibers, we were able to reduce the amount of bleached softwood kraft pulp by at least 5% in the final product. Fungal pretreatment reduced brightness, but brightness was restored to the level of bleached control with 60% more hydrogen peroxide. The economics of biomechanical pulping look attractive.

/pdf/biomechanical-pulping-a-mill-scale-evaluation-3q65b65ahl.pdf

Biomechanical pulping: a mill-scale evaluation

Biopulping is defined as the treatment of wood chips with lignin-degrading fungi prior to pulping. Fungal pretreatment prior to mechanical pulping reduces electrical energy requirements during refining or increases mill throughput, improves paper strength, reduces the pitch content, reduces cooking time for sulfite pulping, and reduces the environemntal impact of pulping. Our recent work involved scaling up the biopulping process toward the industrial level, investigating both the engineering and economic feasibility of the technology. We envision the process to be done in either a chip-pile or silo-based system for which several factors need to be considered : the degree of decontamination, a hospitable environment for the fungus, and the overall process economics. Currently, treatment of the chips with low-pressure steam is sufficient for decontamination. Furthermore, a simple, forced ventilation system can be used to maintain the proper temperature, humidity, and moisture content throughout the chip bed, thus promoting uniform growth of the fungus. The pilot-scale trial resulted in the successful treatment of 4 tons of wood chips (dry weight basis), with results comparable to those on a laboratory scale. For mechanical pulping, a 2-week treatment results in approximately 30% energy savings, which, considering the additionai equipment and operating costs, results in an overall savings of US$ 10-20 per ton of pulp in a chip-pile system. Larger, 40-ton trials were also successful, with energy savings and paper properties comparable with the laboratory scale. Application : biopulping technology produces stronger mechanical pulps together with energy savings, resulting in substantial economic savings.

New technology for papermaking : commercializing biopulping

Recent Developments in Biopulping Technology at Madison, WI

An analysis is given of various aspects of the design of crystallization-based separation processes. A literature review is included for each of the different themes treated in the study. Special emphasis is placed on the usefulness of the relative composition diagram as a tool for identification of possible flow sheets for separations based on fractional crystallization. A series of rules are derived that may be of practical value in the use of the relative composition diagram. Illustrative examples are included that present the advantages and limitations of this methodology. Results are compared with those obtained from the literature where available. © 2006 American Institute of Chemical Engineers AIChE J, 52: 1754 –1769, 2006

http://cepac.cheme.cmu.edu/pasi2011/library/cisternas/On_the_design_of_fractional_crystallization_process.pdf

Ross E. Swaney

Papers

Optimization of process plant layout with pipe routing

Biomechanical pulping: a mill-scale evaluation

New technology for papermaking : commercializing biopulping

Recent Developments in Biopulping Technology at Madison, WI

On the design of crystallization‐based separation processes: Review and extension