Relationship Between Microbes and the Environment for Sustainable Ecosystem Services, Volume 3: Microbial Tools for Sustainable Ecosystem Services

By Ajay Kumar

Relationship Between Microbes and Environment for Sustainable Ecosystem Services, Volume Three: Microbial Tools for Sustainable Ecosystem Services promotes advances in sustainable solutions, value-added products, and fundamental research in microbes and the environment. Topics include advanced and recent developments in the use of microbes for sustainable development. Volume Three includes concepts and applications of microbes in ecosystem services, with a focus on sustainable practices. The book will include case studies and utility of microbes on both geographical and production system-wide considerations.

This book provides reference information ranging from the description of various microbial applications for the sustainability in different aspects of food, energy, environment industry and social development. This book will be helpful to environmental biotechnology scientists, industrial professionals and experts working in the field of microbiology.

• Covers the latest developments, recent applications and future research avenues in microbial biotechnology for sustainable development
• Includes expressive tables and figures with concise information about sustainable ecosystem services
• Provides a wide variety of applications and modern practices of harnessing the potential of microbes in the environment

• Language: English
• Publisher: Elsevier Science
• Release date: Nov 26, 2022
• ISBN: 9780323910668

Book preview

Preface

Ecosystem services offer benefits to humans, reiterating their reliance on nature, and frame the decisions that emphasize the enduring value of nature to our well-being. They are the direct and indirect contributions of ecosystems to human well-being, as they support our survival and quality of life. This book, Relationship Between Microbes and Environment for Sustainable Ecosystem Services, Volume 3: Microbial Tools for Sustainable Ecosystem Services, presents the advances in sustainable solutions, value-added products, human nutrition, and fundamental research on microbes and the environment. The endeavor of the book is to present advanced information on various microbial applications for sustainability in different aspects of food, energy, environment, industry, and social development. It includes concepts and applications of microbes in ecosystem services focusing on sustainable practices. This book will be helpful to scientists, experts, and industry professionals working in the field of microbe-based products. The book covers the latest biotechnological interventions for harnessing microbial aspects on a large scale for waste utilization and management. This volume will serve as excellent, authoritative information and will include case studies about the utility of microbes in widespread considerations. The book includes a wide variety of approaches and modern practices for harnessing the potential of microbes in the environment. This volume serves as an excellent reference and provides a holistic approach to the most recent advances in applying various microbes as a biotechnological tool for a vast range of sustainable applications, modern practices, and exploring futuristic strategies to harness its full potential.

This volume will be useful for environmental biotechnology scientists, industrial professionals, and experts working in microbiology to understand various microbial tools and their applications to achieve sustainable ecosystem services. We are honored that leading scientists with extensive, in-depth experience and expertise in the use of microbial biotechnology for sustainable practices took the time and effort to contribute these excellent chapters.

We thank the Elsevier team for their generous assistance, constant support, and patience in initiating the volume. We are also grateful to our esteemed friends, well-wishers, faculty colleagues, and the management of Lovely Professional University, India, and Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel.

Jastin Samuel, Lovely Professional University, India

Ajay Kumar, Volcani Center, Rishon LeZion, Israel

Joginder Singh, Lovely Professional University, India

Chapter 1: Clean energy production by microorganisms: A sustainable approach

Pritam Bajirao Patil; Debapriya Sarkar; Angana Sarkar    Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha, India

Abstract

In the current century, the present energy demand is expected to be increased approximately by threefold, which is expected not to be fulfilled by fossil fuels, especially considering that the fossil fuel reservoir is getting depleted day by day. In this current scenario, biofuel and bioenergy produced by different microbes would play a key role in sustaining the energy demand in the coming era. The clean production of biofuel includes the production of biodiesel, bioethanol, bio-butanol as well as bio-hydrogen, whereas microbial fuel cells (MFCs) can produce bioelectricity, which is considered the cleanest bioenergy. Among these, biodiesel and bioethanol are the most dominating biofuels being produced in the present era. As per a report published in 2018, the United States is a leading producer of both bioethanol and biodiesel (60.79 billion liters per year and 7903.25 million liters per day). According to the USDA, corn is used as the primary feedstock for bioethanol production, whereas soybean is used as the primary feedstock for biodiesel production. Brazil stands as the second-highest biofuel producer, producing 30.755 billion liters of ethanol in 2018 and about 5745 million liters of biodiesel per year. Sugarcane and sugarcane bagasse are chiefly used for bioethanol production and soybean for biodiesel production in Brazil. Contradictorily, Germany produced 3.2 million tonnes of biodiesel in 2018, using rapeseed and cooking oil as the primary feedstock. Like bio-hydrogen and bio-butanol, other biofuels have complexities such as low productivity, high production cost, producer organism, and substrate rigidity that limit them within the lab scale. Biodiesel and bioethanol production has different improved aspects of fulfilling the worldwide demand. The electricity generation from MFC was also found insufficient to fulfill large-scale demand. In this current chapter, different aspects of biofuel and bioenergy production will be studied elaborately, and different ongoing research studies will be addressed to improve the existing process.

Keywords

Bioethanol; Biodiesel; Bio-butanol; Bio-hydrogen; Microbial fuel cells; Fermentation

1: Introduction

Clean energy, as the name suggests, is a type of energy that does not contribute to the pollution of our atmosphere by any means. It is also referred to as renewable energy as it comes from the sources that are replenished continuously. The need for clean energy has increased tremendously in the last decade as pollution levels have risen to critical levels. India was the third largest CO2 emitter in 2018, along with China in the first, followed by the United States in the second position. India produced around 2.65 billion metric tonnes of CO2 in 2018 (Web reference 1, n.d.). According to the World Health Organization, 14 out of the world's 15 most polluted cities are in India (Web reference 2, n.d.).

According to their sources, there are different types of clean energy, as shown in Fig. 1. Solar energy is what we harvest from the sun, i.e., light and heat are converted into energy. This conversion is done using different technologies. It is the cheapest energy source compared with other sources due to different reasons such as low maintenance cost, cost-effective technology, etc. China is the leading producer of solar energy, followed by the United States, Germany, and Japan (Jäger-Waldau, 2020). But the biggest demerit of solar energy is that it requires large amounts of land to keep solar panels and its weather dependency (Rabaia et al., 2020).

Fig. 1

Fig. 1 Types of clean energy.

Wind energy is also a form of solar energy in which wind is used to generate electricity. The wind has kinetic energy converted into mechanical energy by the turbines, and then this mechanical energy is converted into electricity by a generator. India is the fourth largest producer of wind energy after the United States, China, and Germany. The main problem with wind energy is that it requires a large land capacity. They are often installed in remote locations, which are far from the customer; thus, cost of transportation increases (Web reference 3, n.d.).

Hydro energy is a form of energy that harnesses the power of water in motion to produce electricity. In this kind of energy, the potential energy of water is converted into kinetic energy, which is utilized to spin the turbine, which in turn is used by the generator to produce electricity. The main problem with this is that it requires a large amount of land to store water, and the initial capital required to construct a dam facility is very high compared with other types (Web reference 4, n.d.).

In tidal energy, the kinetic energy of tides and the rise and fall of seawater are utilized to produce electricity. This resembles the wind energy in turbines, but tidal turbines are made underwater. Gravity plays an important role in the formation of tides. This is more reliable than solar and wind as tides are more predictable than the sun and wind. But this technology is still under development and has a lot to research and build (Web reference 5, n.d.).

Geothermal energy is the heat within the earth utilized in boilers to produce steam, which is utilized to run turbines. This energy has been used for decades for different purposes rather than electricity. The main problem with this is that they have to be built at specific locations such as tectonic plate boundaries to extract the heat (Web reference 6, n.d.).

Biomass energy is the only form of organic energy. It is harnessed from living or non-living organisms. Source contains microorganisms, plants, animals, etc. These sources are called biomass feedstocks. This energy is then converted into electricity and other purposes, mainly biofuels (Web reference 7, n.d.).

All of the above energy sources are non-harmful to the environment, but every form has its own drawbacks. Nowadays, biomass energy is being taken into consideration by many researchers and governments for the production of various fuels such as bioethanol, biodiesel, bio-butanol, etc., being used instead of non-renewable sources such as petrol, diesel, etc. In this book chapter, we will be focusing on microbial production, present approaches for it, and prospects for the same.

2: Clean energy from microorganisms

Microorganisms have enormous potential for different kinds of things such as the production of different kinds of products, biorefineries, waste treatment, etc. Also, they have adapted themselves to different kinds of habitats. This adaptation has helped them utilize different kinds of carbon sources and produce different kinds of products, including biofuels. Mostly, microbes capable of photosynthesis have a higher potential for production. In biofuels, the most common are bioethanol, biodiesel, bio-butanol, and bio-hydrogen (Donohue and Cogdell, 2006). All these are alternatives to the currently available fuels derived from non-renewable fossil fuels. They also pollute the environment by releasing greenhouse gases after their combustion. Another new technology studied extensively is the microbial fuel cell (MFC), in which direct electricity generation through microbes is taken into consideration. All these will be discussed later in this chapter.

2.1: Types of clean energy by microbes

As shown in Fig. 2, there are mainly two types of clean energy derived from a microbe, namely biofuels and electricity. Different types of biofuels can be utilized commercially, but the main focus is on biodiesel, bioethanol, bio-butanol, and bio-hydrogen. In the case of electricity generation, MFCs are in research.

Fig. 2

Fig. 2 Types of clean energy from microbes.

2.1.1: Biodiesel

It is an alternative to petroleum diesel. It can be harnessed from animal fats and vegetable oil or can be produced by microorganisms such as algae. It is an eco-friendly choice as fuel over conventional diesel as it does not produce any greenhouse gases and is biodegradable (Krawczyk, 1996). Also, nowadays, the prices of petroleum products are rising tremendously; hence to tackle that, biodiesel can be a good option. The main advantage of biodiesel is that it is made from renewable sources. Therefore, its supply will not diminish. Chemically it resembles the structure of fatty acid with alkali esters.

Existing process of production and involvement of microorganisms

Currently, biodiesel is being produced from grease, vegetable oils, animal fats, and microbes. There are different approaches to its production from all the above sources. Oils and fats are mostly triglycerides, converted into glycerine by the esterification reaction (Fukuda et al., 2001). This reaction is a three-step process. In first step, triglyceride is reacted with an alcohol to produce diglyceride. Then this diglyceride is converted into monoglyceride and then into glycerine. In all these steps, esters are produced (Miguel et al., 2001). The first step is the catalyst-driven step; hence, the rate and other parameters of this reaction depend on the choice of catalyst. There are many choices for a catalyst such as an alkali, acid, lipase, etc.

Microorganisms, mainly algae, are used to produce biodiesel as they have a high capacity to store oil. The main advantage of using algae is that they are photosynthetic, which means they can utilize solar energy to survive. Solar energy is converted finally into carbohydrates through many steps of the Calvin cycle. Algae have higher efficiency in using solar energy than crops, which are mainly used to produce biodiesel, hence are more efficient in the storage of oils (Vasudevan and Briggs, 2008). Bacteria are considered to produce micro-diesel through genetic modifications (Kalscheuer et al., 2006). Microbes that can store lipids are called oleaginous microbes. They can store up to 20% of their dry weight, but in nitrogen limit conditions, this ability can be increased to 70% (Rossi et al., 2011). Most of the current biodiesel is produced from vegetable oils, but the alcohol needed to catalyze the first step can be procured from the bacterial fermentation processes (Kildiran et al., 1996).

Drawbacks of existing process regarding the producer organisms

The current process for the production of biodiesel has many problems in many areas. The main consideration is the unavoidable water content, which leads to corrosion. Glycerol produced during production creates the problem of deposition in certain areas (Antoni et al., 2007). In consideration of production from algae, the storage of oil depends from species to species. High oil storing algae have a very slow growth rate, while low oil storing algae have a higher growth rate. This is because the storage of solar energy in oil rather than carbohydrates is a time-consuming process, and the production of oil happens when algae are stressed, particularly nutritionally. But the main problem with limiting nutrients is that it also reduces the growth rate, which in turn hampers the overall process making it more costly (Vasudevan and Briggs, 2008). Also, the substrates required to grow the microbes and then the lipid extraction process are very costly, increasing their commercial cost (Lardon et al., 2009).

2.1.2: Bioethanol

It is also a green alternative to traditional petroleum fuels. The low cost of reagents and production also becomes a more economical alternative to petroleum products. Production of ethanol has a long historical background being one of the first products to be produced using microbes. For many years, yeast has been used prominently for the production of ethanol (Madhavan et al., 2011), but now many bacterial fermentation processes have been deduced for the same. Bioethanol production has been divided into three generations depending on the type of substrate used. In the first generation, food crops such as sugarcane and grains are used. In the second generation, the by-products of crop industries are used, such as sugarcane bagasse (Robak and Balcerek, 2018). In the third generation, ethanol production from various sugars is being done (Shields and Boopathy, 2011). Currently, many new substrates are under trial for the production such as fruit waste, agricultural waste, etc., compared with the most widely used biofuel today, i.e., gasoline, ethanol has higher octane number, higher flame speeds, and higher heats of vaporization, broader flammability limits hence higher compression ratio, leaner engine, and shorter burn time. Hence, its use as fuel has many advantages over gasoline. Also, as it is an oxygenated fuel, it produces low greenhouse gases compared with other fuels (Balat et al., 2008).

Existing process of production and involvement of microorganisms

The existing process of ethanol production has different ways, such as direct chemical production and the fermentation process using microbes. The chemical process involves the reaction of ethylene with steam at high temperatures and pressure, resulting in harmful gas production. Hence, this is not used widely. Production by fermentation has many advantages over chemical processes such as cost-effective, no harmful by-products, etc. (Gnansounou and Dauriat, 2005). Many substrates can be used for the production through fermentation such as sugarcane, sugarcane bagasse, corn, cereals, etc. These feedstocks that can be converted into sugar or sugar-like molecules can also be used such as cellulosic substrates and lignin-containing substrates. The substrate can be classified into three types: sucrose-containing (sugarcane, beet), starch-containing (corn, wheat), and lignocellulosic (grasses, wood) (Malça and Freire, 2006). Most of the fermentation processes have common steps, such as processing feedstock to form soluble sugars and then using this pre-treated substrate for fermentation using the specific microbes or consortium. After production, ethanol is purified using distillation methods at large scales. Fermentation can be done in simultaneous saccharification and fermentation, and the other way is the separate hydrolysis and fermentation. In the former process, only a single reactor is used for both saccharifications of raw material and then followed by fermentation. So, this is more cost-effective and has higher productivity (Buaban et al., 2010). Latter one is the process in which hydrolysis and fermentation are done in two different reactors, mainly first the hydrolysis and then its fermentation (Bjerre et al., 2000). Many microbes have been reported to date for the production of ethanol such as Saccaromyces cerevisea, Pichia pastoris, Mucor indicus, Pachysolen tannophilus, Pichia stipites, C. shehatae, Candida brassicae, Zymomonas mobilis (Katahira et al., 2006; Jeffries and Jin, 2000).

Drawbacks of existing process regarding the producer organisms

Although the current process for ethanol production is well studied and optimized for the best results, there are still many challenges that are being faced. The main challenge faced is the contamination by different species during the fermentation process. As these fermentation processes run for long times and the volumes are large, it is difficult to maintain sterilization. Due to contamination, productivity decreases significantly and production of by-products increases. Sometimes these by-products may be harmful to the major producer of ethanol, further affecting its production (Cabrini and Gallo, 1999). The main contaminants of this process are the Lactobacillus and Bacillus (Lucena et al., 2010). Another drawback of the current process is the production of large volumes of vinasse. Vinasse is the stillage that remains after removing ethanol (Mutton et al., 2010). However, many efforts are taking place to tackle the drawbacks, including genetic manipulation of strains, building different systems, etc.

2.1.3: Bio-butanol

This is another type of biofuel that has been produced for many years. Its production started at the time of Pasteur. The main drift in butanol production started when we faced scarcity in natural rubber as synthetic rubber can be prepared from butanol and isoamyl alcohol. Nowadays, fermentation is the main approach for butanol production, and its production comes under the category of solvent fermentation. Butanol has many advantages over ethanol as it can be used in current gasoline engines without any modifications. It has a 30% higher volumetric energy density than ethanol. Also, it can be blended with gasoline without any phase separation due to its low vapor pressure (Amiri and Karimi, 2019). Hence due to all these properties, butanol has gained importance in biofuels.

Existing process of production and involvement of microorganisms

Butanol production through fermentation started in 1913 using a Bacillus spp. with potato as substrate as the strain used at that time was not able to ferment corn and other substrates. Then in 1916, the whole process was shifted to another process called Weizmann's process, which used another strain that was able to ferment corn and other substrates. The strain was then further characterized and termed Clostridium acetobutylicum (Jones et al., 1986). Currently, this strain is used most widely. Clostridia genus has the most abundant species of microbes, which produce butanol with high efficiency, e.g., Clostridium beijerinckii, Clostridium saccharoacetobutylicum, Clostridium aurantibutyricum, Clostridium sporogenes, Clostridium saccaroperbutylacetonicum, Clostridium pasteurianum (Huang et al., 2010). Nowadays, many different types of raw materials are used in fermentation such as corn, wheat, switchgrass, cassava, etc. Different strains can utilize different substrates and have different productivities. Many different processes such as batch, fed batch, continuous, free cell continuous, immobilized continuous systems are tried for the production, and different results were obtained with each system having its drawbacks and advantages (Kumar and Gayen,