available over the Earth. Hence, bioethanol may have a low production value
compared to other fuels. It has a high octane number as well as is an eco-friendly
fuel (Chang and Lin 2004; Sarkar et al. 2012; Manish and Banerjee 2008; Limayen
and Ricke 2012). Nowadays, it can be generated from various types of biomasses
such as algal, bacterial, fungal, plant, and agricultural wastes. It is also produced
from several types of edible and non-edible oils such as mustard oil, soybean oil, and
corn oil (Forte et al. 2017; Whitaker et al. 2018; Gonzalez-Garcia et al. 2019).
Microalgae are the major source of bioethanol product. Microalgae produce a large
amount of bioethanol and other biofuels (Porth and El-Kassaby 2015). The production of bioethanol can be improved through genetic engineering in the wild
microalgal species (Kuhad and Singh 1993; Manish and Banerjee 2008; Balan
2014).
Nanotechnology has an important role in the bioethanol industries. Nanoscale
particles provide more areas for chemical and biological reaction. Cherian et al.
investigated that MaO 2 enhance the bioethanol generation from biomass of sugarcane leaves at optimum parameters (Cherian et al. 2015). The small size and bigger
surface area of the MnO 2 have more binding sites for enzymes and other reactive
molecules and increase the production of ethanol.
2.4.3 Biogas
Biogas is a cost-effective and eco-friendly biofuel. Methane is the main component
of biogas, and it is produced from the digestion of organic materials. Several
microbial species such as methanogens are involved in the biogas production
(Romero-Guiza et al. 2016; Aryal et al. 2018). There are several processes involved
in the biogas production. Hydrolysis is the main step of biogas production. In the
hydrolysis process, the breakdown of substrate takes place in the presence of a
suitable digestion system. The hydrolysis step includes the digestion of a large
molecule such as protein and carbohydrates into amino acids and simple sugar,
respectively (Romero Victorica et al. 2020). The second most important step is
acidogenesis. The third main step is acetogenesis. In the acetogenesis acetic acid
envolves in several microbial activities. The fourth and important step is
methanogenesis. Methanogenesis is the production of methane gas in the biogas
production system. The methane gas is produced from several methanogenic bacteria (Mao et al. 2015; Arias et al. 2020; Buitron et al. 2014; Waqas et al. 2020; Sekoai
et al. 2016). The acidogenesis process is responsible for the digestion of sugar and
amino acids and produces CO2, hydrogen, and alcohol. There are several pathways
involved in the acidogenesis process. The biogas is produced from various microbial
pathways, and the growth of methanogenic bacteria required low concentration of
hydrogen in the growth medium (Hankamer et al. 2007; Rupprecht et al. 2006).
Biogas produced from several biological wastes is considered as a safe, clean, and
zero waste emission fuel. It is also considered as an alternative option of LPG and
can replace the use of LPG in the future.
2 Microbiological Aspects of Bioenergy Production: Recent Update and Future. . .
41
compared to other fuels. It has a high octane number as well as is an eco-friendly
fuel (Chang and Lin 2004; Sarkar et al. 2012; Manish and Banerjee 2008; Limayen
and Ricke 2012). Nowadays, it can be generated from various types of biomasses
such as algal, bacterial, fungal, plant, and agricultural wastes. It is also produced
from several types of edible and non-edible oils such as mustard oil, soybean oil, and
corn oil (Forte et al. 2017; Whitaker et al. 2018; Gonzalez-Garcia et al. 2019).
Microalgae are the major source of bioethanol product. Microalgae produce a large
amount of bioethanol and other biofuels (Porth and El-Kassaby 2015). The production of bioethanol can be improved through genetic engineering in the wild
microalgal species (Kuhad and Singh 1993; Manish and Banerjee 2008; Balan
2014).
Nanotechnology has an important role in the bioethanol industries. Nanoscale
particles provide more areas for chemical and biological reaction. Cherian et al.
investigated that MaO 2 enhance the bioethanol generation from biomass of sugarcane leaves at optimum parameters (Cherian et al. 2015). The small size and bigger
surface area of the MnO 2 have more binding sites for enzymes and other reactive
molecules and increase the production of ethanol.
2.4.3 Biogas
Biogas is a cost-effective and eco-friendly biofuel. Methane is the main component
of biogas, and it is produced from the digestion of organic materials. Several
microbial species such as methanogens are involved in the biogas production
(Romero-Guiza et al. 2016; Aryal et al. 2018). There are several processes involved
in the biogas production. Hydrolysis is the main step of biogas production. In the
hydrolysis process, the breakdown of substrate takes place in the presence of a
suitable digestion system. The hydrolysis step includes the digestion of a large
molecule such as protein and carbohydrates into amino acids and simple sugar,
respectively (Romero Victorica et al. 2020). The second most important step is
acidogenesis. The third main step is acetogenesis. In the acetogenesis acetic acid
envolves in several microbial activities. The fourth and important step is
methanogenesis. Methanogenesis is the production of methane gas in the biogas
production system. The methane gas is produced from several methanogenic bacteria (Mao et al. 2015; Arias et al. 2020; Buitron et al. 2014; Waqas et al. 2020; Sekoai
et al. 2016). The acidogenesis process is responsible for the digestion of sugar and
amino acids and produces CO2, hydrogen, and alcohol. There are several pathways
involved in the acidogenesis process. The biogas is produced from various microbial
pathways, and the growth of methanogenic bacteria required low concentration of
hydrogen in the growth medium (Hankamer et al. 2007; Rupprecht et al. 2006).
Biogas produced from several biological wastes is considered as a safe, clean, and
zero waste emission fuel. It is also considered as an alternative option of LPG and
can replace the use of LPG in the future.
2 Microbiological Aspects of Bioenergy Production: Recent Update and Future. . .
41