New and Future Developments in Microbial Biotechnology and Bioengineering

Aspergillus System Properties and Applications

Vijai Kumar Gupta, Vijai Kumar Gupta

• Publisher: Elsevier
• Year: 2016
• ISBN:
  9780444635136
• Topic: Scienze biologiche
• Subtopic: Microbiologia

New and Future Developments in Microbial Biotechnology and Bioengineering: Aspergillus System Properties and Applications provides information on emerging issues related to recent advancements in aspergillus research and its applications in bioprocess technology, chemical engineering, genome biology, molecular taxonomy, secondary and metabolite production, industrial process and biofuels/bioenergy research, and alternative fuel development. The book covers the various novel enzymes secreted by these fungi and their specific use in the food, textile, pulp and paper, biocellulosic ethanol production, and other industries.

The book describes research and experimentation on aspergillus activity and directly connects them to their use in bioprocess technology, chemical engineering, bioremediation process, secondary metabolite production, pharmaceutical processes, protein production, industrial process, biofuels/bioenergy research, and alternative fuel development. Readers will find this book to be an indispensable resource for biotechnologists, biochemical engineers, biochemists, microbiologists, bioinformatics researchers, and other biologists who are interested in learning about the potential applications of these fungi.

• Compiles available, up-to-date information on recent developments made in the study of aspergillus system properties
• Contains global content from pioneering international authors
• Presents current research efforts and links them to various applications, including uses in foods, textiles, pulp and paper, and in biocellulosic ethanol production
• Provides an indispensable resource for biologists who are interested in learning about the potential applications of the fungi aspergillus

Section V

Applications

Outline

Chapter 9 Enzyme System from Aspergillus in Current Industrial Uses and Future Applications in the Production of Second-Generation Ethanol

Chapter 10 Advances in Cultivation Strategies of Aspergillus for Production of Enzymes Involved in the Saccharification of Lignocellulosic Feedstocks

Chapter 11 β-Glucosidase From Aspergillus

Chapter 12 Regulation and Heterologous Expression of Lignocellulosic Enzymes in Aspergillus

Chapter 13 Aspergillus Enzymes for Textile Industry

Chapter 14 Biosynthesis of Nanoparticles by Aspergillus and Its Medical Applications

Chapter 15 Role of Aspergillus in Bioremediation Process

Chapter 16 Aspergillus Enzymes for Food Industries

Chapter 17 Applications of Aspergillus in Plant Growth Promotion

Chapter 18 Aspergillus in Biomedical Research

Chapter 19 Aspergillus Applications in Cancer Research

Chapter 20 Protein Production: Quality Control and Secretion Stress Response

Chapter 21 Bioremediation of Arsenic Using an Aspergillus System

Chapter 22 Secondary Metabolite Diversity of the Genus Aspergillus: Recent Advances

Chapter 9

Enzyme System from Aspergillus in Current Industrial Uses and Future Applications in the Production of Second-Generation Ethanol

M.L.T.M. Polizeli, A.C. Vici, A.S.A. Scarcella, M. Cereia and M.G. Pereira, Universidade de São Paulo, Ribeirão Preto, SP, Brazil

Abstract

Multiple fungal glycoside hydrolases can be used in biorefinery processes in the conversion of biomass into biofuels. The main polymers of plant biomass are cellulose and hemicellulose, which, together with lignin, constitute the most abundant organic compounds present in nature. Cellulose and hemicellulose are hydrolyzed by cellulolytic and hemicellulolytic enzymatic systems to monomers as glucose and xylose, respectively, which may be fermented by yeasts into second-generation ethanol. Aspergillus is a distinguished fungal genus, important in the production of enzymes that are able to degrade plant cell wall, which is a key step in the bioconversion of sugarcane biomass. This chapter will describe several species of Aspergillus as excellent producers of fibrolytic enzymes as well as current advances in the understanding of glycoside hydrolases, auxiliary activities, and important properties for the conversion of biomass into second-generation ethanol.

Keywords

Aspergillus; enzyme; filamentous fungi; cellulase; xylanase; accessory proteins; second-generation ethanol; biomass; biorefinery

Introduction

Currently, features such as climate change, scarcity of petroleum reserves, and increase in the costs of fuels have stimulated an unprecedented research into the production of alternative fuels, preferably from renewable energy sources. Beyond these reasons, it is necessary to be aware of environmental preservation, what justifies new viable technologies for the production of fuels.

The replacement of petroleum-derived fuels by biofuels could contribute to reduce environmental impacts and lignocellulosic biomass from sugarcane has been identified as an excellent alternative among the potential sources of biofuel production.

Ethanol production from sucrose corresponds to one-third of sugarcane biomass. The other two-thirds correspond to bagasse and straw. Currently, bagasse is used as a fuel, being burned in boilers to fulfill the demands of industrial energy, but statistics show that there is still a surplus of 30% of this product. Straw is usually burned before harvest in order to facilitate this process, or it is left in the field to be used as a fertilizer and pest control (Leal et al., 2013; Pereira et al., 2015).

There is a technological challenge to be overcome so that straw does not undergo decomposition in the field (Dias et al., 2013; Gnansounou et al., 2015). One solution is to take advantage of the sugar contained in the bagasse and straw to produce second-generation ethanol—named this way in reference to the oldest form of production, made from sugarcane juice. Second-generation ethanol is considered the biofuel with the greatest potential to replace fossil fuels and may also increase productivity without changing the planted area (Santos et al., 2011; Pereira et al., 2015).

Brazil, followed by India, China, and Thailand are the largest sugarcane producers in the world. A large extension of its territory is destined to the cultivation of sugarcane. The crop of 2014/15 was estimated in 613 million tons of sugarcane to be processed by Brazilian sugar-alcohol mills, resulting in an ethanol production of approximately 28 billion liters and an output of sugar of about 36 million tons. In the production of first-generation ethanol each ton of processed sugarcane bagasse generates 140 kg of bagasse and 140 kg of trash, on a dry base (db) (Oliveira et al., 2013; Pereira et al., 2015).

Bagasse and straw from sugarcane are constituted by lignocellulosic components (cellulose, hemicellulose, and lignin) connected in a complex manner in the cell wall. Hemicellulose is mainly composed by xylose (five-carbon sugar), and few industries use this. Lignin has a high calorific potential to produce energy that can be used in industrial processes, such as ethanol production. This intricate architecture and the recalcitrant nature of the biomass result in a technological barrier for second-generation ethanol production.

In order to obtain the complete degradation of cellulose and hemicellulose up to, especially, glucose, it is suggested to subject sugarcane bagasse to physical and chemical pretreatments. For example, steam explosion, acid and alkali treatments, followed by the use of efficient enzymatic systems. Doing so would increase sugar yields that could be used by yeasts in the fermentation process, which is the final phase of bioethanol production (Oliveira et al., 2013).

This chapter will focus on the components and the functional properties of the cellulolytic and hemicellulolytic systems produced by Aspergilli, which are important filamentous fungi related to the production of enzymes that degrade plant cell wall components, completing the enormous spectrum of possibilities where enzyme systems can be used in current industrial applications.

Biodiversity and Bioprospecting

Biodiversity comprises the variability of life on Earth, including genetic variability in populations and species; the variability of flora and fauna species, macroscopic fungi and microorganisms, the variability of ecological functions performed by organisms in the ecosystems and, the variability of communities, habitats, and ecosystems formed by organisms (http://www.sobiologia.com.br/conteudos/Seresvivos/Ciencias/biodiversidade.php). The network of living organisms, through a combination of biochemical activities of its plants, animals, and microorganisms, unifies physical and chemical atmosphere, geosphere, and hydrosphere in an environmental system including millions of species.

All the benefits produced by this network can be used to overcome the energy problems the world faces today, generating solutions and profits. On the other hand, local and global environmental changes can generate indirect effects on biodiversity influencing the intensity and magnitude of existing stressors, such as invasive species, rainfall, fire regime, structure, functions and processes of ecosystems, leading to biodiversity loss, as well as genetic variety loss and species extinction, especially in vulnerable and fragmented ecosystems.

It is estimated that only 10% (2.0 million) of the species existing in the world are known. Brazilian biodiversity is estimated to be between 15 and 25% (200,000 species) of global biodiversity (most of these are large taxa). However, there is a big gap of knowledge to be remedied and these data justify the ...