Optimization of dilute acid and alkaline peroxide pretreatment to enhance bioethanol production from wheat straw by co-fermentation (original) (raw)
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Lignocellulosic biomass to bioethanol, a comprehensive review with a focus on pretreatment
Renewable and Sustainable Energy Reviews, 2013
Pretreatment technologies are aimed to increase enzyme accessibility to biomass and yields of fermentable sugars. In general, pretreatment methods fall into four different categories including physical, chemical, physico-chemical, and biological. This paper comprehensively reviews the lignocellulosic wastes to bioethanol process with a focus on pretreatment methods, their mechanisms, advantages and disadvantages as well as the combinations of different pretreatment technologies. Moreover, the new advances in plant "omics" and genetic engineering approaches to increase cellulose composition, reduce cellulose crystallinity, produce hydrolases and protein modules disrupting plant cell wall substrates, and modify lignin structure in plants have also been expansively presented.
3 Biotech, 2015
Second-generation bioethanol can be produced from various lignocellulosic biomasses such as wood, agricultural or forest residues. Lignocellulosic biomass is inexpensive, renewable and abundant source for bioethanol production. The conversion of lignocellulosic biomass to bioethanol could be a promising technology though the process has several challenges and limitations such as biomass transport and handling, and efficient pretreatment methods for total delignification of lignocellulosics. Proper pretreatment methods can increase concentrations of fermentable sugars after enzymatic saccharification, thereby improving the efficiency of the whole process. Conversion of glucose as well as xylose to bioethanol needs some new fermentation technologies to make the whole process inexpensive. The main goal of pretreatment is to increase the digestibility of maximum available sugars. Each pretreatment process has a specific effect on the cellulose, hemicellulose and lignin fraction; thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. The cost of ethanol production from lignocellulosic biomass in current technologies is relatively high. Additionally, low yield still remains as one of the main challenges. This paper reviews the various technologies for maximum conversion of cellulose and hemicelluloses fraction to ethanol, and it point outs several key properties that should be targeted for low cost and maximum yield.
Frontiers in bioscience (Scholar edition), 2018
The future supply of energy to meet growing energy demand of rapidly exapanding populations is based on wide energy resources, particularly the renewable ones. Among all resources, lignocellulosic biomasses such as agriculture, forest, and agro-industrial residues are the most abundant and easily available bioresource for biorefineries to provide fuels, chemicals, and materials. However, pretreatment of biomass is required to overcome the physical and chemical barriers that exist in the lignin-carbohydrate composite and pretreatment facilitate the entry of biocatalysts for the conversion of biomass into fermentable sugars and other by-products. Therefore, pretreatment of the biomass is necessary prerequisite for efficient hydrolysis of lignocelluloses into different type of fermentable sugars. The physiochemical, biochemical and biological pretreatment methods are considered as most promising technologies for the biomass hydrolysis and are discussed in this review article. We also d...
The conversion of lignocellulosic biomass to bioethanol: pretreatment technology comparison
IOP Conference Series: Earth and Environmental Science
The barrier to realising the potential of lignocellulosic bioethanol is the recalcitrance of cellulosic biomass. Overcoming this biomass recalcitrance is the key challenge to large scale production of lignocellulosic bioethanol. Pretreatment is an important and critical step that enables enzyme hydrolysis of lignocellulose conversion to ethanol. Finding a pretreatment method for reducing the high recalcitrance via cost-effective pretreatment methods would therefore be of great benefit. This study aims at investigating the effect of pretreatment on delignification process of sugarcane bagasse and oil palm trunk. Two methods of pretreatment were compared i.e. alkaline hydrogen peroxide pretreatment (1% and 5% H2O2) and subcritical water pretreatment (170°C, 2.2 MPa) for the effectiveness of reducing the lignin content. Scanning Electron Microscopy (SEM) analysis was also performed to investigate the effect of pretreatment on surface of lignocellulosic biomass. It was observed that alk...
Lignocellulosic ethanol production: current practices and recent developments
2011
Production of renewable fuels, especially bio-ethanol from lignocellulosic biomass, holds remarkable potential to meet the current energy demand as well as to mitigate greenhouse gas emissions for a sustainable environment. Present technologies to produce bioethanol largely depend on sugarcane and/or starch based grains and tubers (mainly corn, potatoes). This is partly due to ease of substrate handling and processing. On the other hand, use of sugarcane and food grains to produce bio-ethanol has caused significant stress on food prices and food security. Accordingly, the recent focus has been on lignocellulosic materials as a source for bio-ethanol. In fact, many countries are moving towards developing or have already developed technologies to exploit the potential of lignocellulosic materials for the production of bioethanol. This process of ethanol production generally involves hydrolysis of lignocellulosic biomass to fermentable sugars followed by fermentation of such sugars to ethanol. Achieving fermentable levels of sugars from lignocellulosic biomass requires relatively harsh pretreatment processes. The pretreatment process has pervasive impact on the overall operation because the process depends on the choice of lignocellulosic source, the size reduction via grinding, chemical treatment, acid hydrolysis, neutralization and fermentation. Recent advances in the process technologies have made it possible to use simultaneous saccharification and fermentation. In this process cellulase enzyme is the critical reagent as well as the cost determining factor. The advances in biotechnology as related to bioethanol have focused on engineering organisms that are capable of producing ethanol from cellulose, hemicellulose and lignocellulose. Such organisms are expected to be capable of not only degrading cellulose, hemicellulose and lignocellulose to fermentable sugars, but also are able to utilize both pentose and hexose sugars to produce ethanol at a relatively high yield. More recent and emerging approaches in bioethanol production are focused on reducing production costs. This approach uses consolidated bioprocessing schemes in which cellulase production, substrate hydrolysis, and fermentation are all accomplished in a single step. Countries, such as Nepal, that totally depend on the import of fossil fuels cannot ignore the potential of bioethanol derived from lignocellulosic biomass. Nepal is rich in biodiversity and posses variety of energy crops. Accordingly, developing policies and mechanisms that promote bioethanol will go a long-way in reducing the fuel crises in the countries lacking oil resources.
Features of promising technologies for pretreatment of lignocellulosic biomass
Bioresource Technology, 2005
Cellulosic plant material represents an as-of-yet untapped source of fermentable sugars for significant industrial use. Many physio-chemical structural and compositional factors hinder the enzymatic digestibility of cellulose present in lignocellulosic biomass. The goal of any pretreatment technology is to alter or remove structural and compositional impediments to hydrolysis in order to improve the rate of enzyme hydrolysis and increase yields of fermentable sugars from cellulose or hemicellulose. These methods cause physical and/or chemical changes in the plant biomass in order to achieve this result. Experimental investigation of physical changes and chemical reactions that occur during pretreatment is required for the development of effective and mechanistic models that can be used for the rational design of pretreatment processes. Furthermore, pretreatment processing conditions must be tailored to the specific chemical and structural composition of the various, and variable, sources of lignocellulosic biomass. This paper reviews process parameters and their fundamental modes of action for promising pretreatment methods.
Pretreatmentsemployed in lignocellulosic materials for bioethanol production: An overview
Lignocellulosic materials are raw materials with high cellulose content and they constitute the most abundant sources of biomass on planet. They are attractive for their low cost and high availability in diverse climates and places for the bioethanol production, however, the main impediment for its use is the appropriate selection from the technological and economic point of view of the stages of pretreatments and hydrolysis, that allow the breaking down of the lignocellulosic matrix to obtain the necessary substrates in the processes of fermentation. Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol, which have been divided in three groups for its study in: physical-chemical, hydrothermal and biological. The aim of this paper is to analyze the potential of several pretreatment methods for bioethanol production from lignocellulosic materials.
Current Trends in Lignocellulosic Bioethanol Production
International Journal of Applied Sciences and Biotechnology, 2022
In view of crude oil prices, and its environmental issues, utilization of sustainable renewable alternative energies such as biofuels is rapidly progressing in many countries. The increasing global energy demand and depleting fossils fuels sources has led to search alternative clean and renewable fuels. One of the best alternatives to the gasoline is lignocellulosic bioethanol. Recent researches on lignocellulosic bioethanol focuses on advancement of pretreatment techniques for improved sugar yields and decreased inhibitors production. Pretreatment technique with no or less use of chemicals and cost effectiveness is the main purpose of most of the researches. Biological pretreatment techniques produce less fermentation inhibitors than chemical pretreatments. In order to cope with fermentation inhibitors different strategies can be adopted during pretreatment processes. In the course of time, advancements in production process over separate hydrolysis and fermentation have been intro...