Amith Abraham

Potential of rice straw for bio-refining: An overview

The biorefinery approach for the production of fuels and chemicals is gaining more and more attraction in recent years. The major advantages of biorefineries are the generation of multiple products with complete utilization of biomass with zero waste generation. Moreover the process will be economically viable when it targets low volume high value products in addition to high volume low value products like bioethanol. The present review discuss about the potential of rice straw based biorefinery. Since rice is a major staple food for many Asian countries, the utilization of the rice straw residue for fuel and chemicals would be very economical. The review focuses the availability and the potential of this residue for the production of fuel and other high value chemicals.

Recent developments in l-glutaminase production and applications – An overview

l-glutaminases is an important industrial enzyme which finds potential applications in different sectors ranging from therapeutic to food industry. It is widely distributed in bacteria, actinomycetes, yeast and fungi. l-Glutaminases are mostly produced by Bacillus and Pseudomonas sp. and few reports were available with fungal, actinomycete and yeast system. Modern biotechnological tools help in the improved production as well as with tailor made properties for specific applications. Most of the genetic engineering studies were carried out for the production of l-glutaminase with improved thermo-tolerance and salt tolerance. Considering the potential of in vitro applications of l-glutaminase, extracellular enzymes are important and most microbes produce this enzyme intracellularly. Several research and developmental activities are going on for the extracellular production of l-glutaminase. This review discusses recent trends and developments and applications of l-glutaminases.

Molecular improvements in microbial α-amylases for enhanced stability and catalytic efficiency

α-Amylases is one of the most important industrial enzyme which contributes to 25% of the industrial enzyme market. Though it is produced by plant, animals and microbial source, those from microbial source seems to have potential applications due to their stability and economic viability. However a large number of α-amylases from different sources have been detailed in the literature, only few numbers of them could withstand the harsh industrial conditions. Thermo-stability, pH tolerance, calcium independency and oxidant stability and starch hydrolyzing efficiency are the crucial qualities for α-amylase in starch based industries. Microbes can be genetically modified and fine tuning can be done for the production of enzymes with desired characteristics for specific applications. This review focuses on the native and recombinant α-amylases from microorganisms, their heterologous production and the recent molecular strategies which help to improve the properties of this industrial enzyme.

Development of a novel ultrasound-assisted alkali pretreatment strategy for the production of bioethanol and xylanases from chili post harvest residue

A novel ultrasound-assisted alkali pretreatment strategy was developed which could effectively remove lignin and hemicelluloses and improve the sugar yield from chili post harvest residue. Operational parameters that affect the pretreatment efficiency were studied and optimized. Inhibitor analysis of the hydrolyzate revealed that major fermentation inhibitors like furfural, 5-hydroxymethyl furfural as well as organic acids like citric acid, succinic acid and propionic acid were absent. Hence fermentation can be carried out without detoxification of the hydrolyzate. Changes in structural properties of the biomass were studied in relation to the pretreatment process using Scanning Electron Microscopy (SEM) and the changes in chemical composition were also monitored. The biomass pretreated with the optimized novel method could yield 0.428g/g of reducing sugars upon enzymatic hydrolysis. The hydrolyzate obtained by this novel pretreatment strategy was found to be suitable for bioethanol and xylanase production.

First- and Second-Generation Ethanol in India: A Comprehensive Overview on Feedstock Availability, Composition, and Potential Conversion Yields

With imports of crude oil touching 80% of the total requirement, India is a nation heavily dependent on foreign oil. There are serious efforts to replace part of the transportation fuels with renewable alternatives—notably biofuels. Bioethanol from biomass is probably the near-term solution, since the country is dependent on imports for edible oils, which in turn makes the possibility of near-term implementation of biodiesel as a renewable transportation fuel remote. Being an agrarian economy, the country has abundant feedstock for bioethanol production in the form of agricultural residues. The country generates a total of nearly 650 million metric tons (MMT) of lignocellulosic agro-residues annually, and though a major part of it is used for other purposes, there are still huge quantities of the feedstock available as surplus. Major technical bottlenecks in the conversion of lignocellulose to ethanol have been addressed worldwide, and companies claim to have started operation in the production of second-generation ethanol. While these international technologies can be implemented here directly or with modifications, the major challenge in India’s context would be to ensure availability of quality raw material at the sites of production. Sustainability of such industries would depend on the availability of feedstock at affordable prices which inherently involve logistic issues. Understanding the type and amount of biomass available in the country and its geographical location is important in establishing bioethanol industries, as well as the potential of converting these feedstocks to ethanol. The chapter introduces the background of India’s need for bioethanol and why first-generation bioethanol cannot fully cater to the gasoline blending demands of the nation and proceeds to describe the availability of agro-residues as potential feedstock for bioethanol in the country. Data on the generation of agro-residues which form major agricultural crops in the country is provided along with estimates for the consumption of these feedstocks for competing applications. It gives a fair estimate of the surplus biomass availability in the country and gives the possible realistic amounts of ethanol that can be generated from these biomass residues based on primary and secondary data about the compositions and conversion efficiencies. The study shows that there is a potential of producing ~30 billion liters of ethanol annually from surplus agro-residues in the country (estimated at ~175 MMT) even at very conservative calculations. The importance of logistics and collection models suited for the country is also highlighted

Applications of Microbial Enzymes in Food Industry

The use of enzymes or microorganisms in food preparations is an age-old process. With the advancement of technology, novel enzymes with wide range of applications and specificity have been developed and new application areas are still being explored. Microorganisms such as bacteria, yeast and fungi and their enzymes are widely used in several food preparations for improving the taste and texture and they offer huge economic benefits to industries. Microbial enzymes are the preferred source to plants or animals due to several advantages such as easy, cost-effective and consistent production. The present review discusses the recent advancement in enzyme technology for food industries. A comprehensive list of enzymes used in food processing, the microbial source of these enzymes and the wide range of their application are discussed.

Production of Pectinase from Bacillus Sonorensis MPTD1

Seven isolates from spoiled fruits and vegetables were screened for pectinase production using pectin agar plates and the most efficient bacterial strain, MPTD1, was identified as Bacillus sonorensis. Optimisation of various process parameters was done using Plackett-Burman and Box-Behnken designs and it was found that parameters like yeast extract, K2HPO4, incubation time, NaNO3 and KCl have a negative impact on pectinase production. Parameters like pH and MgSO4 and pectin mass fractions have a positive impact on pectinase production. The maximum obtained enzyme activity was 2.43 (μM/mL)/min. This is the first report on pectinase production by Bacillus sonorensis.

Lignocellulosic Biorefinery Wastes, or Resources?

Abstract Lignocellulosic biomass is considered the most important future resource for biofuels and chemicals especially since the world is poised toward a carbohydrate economy. Biorefineries, analogous to petroleum refineries where the carbohydrate polymers are processed to derive sugars, which then can be converted both biologically and chemically to various fuels and chemicals, are no longer a future proposition but a reality. Biomass processing involves multiple steps, some of which involving the use of chemicals and thermal treatment and generating products that do not have direct fuel or chemical value unless separated and purified. These include sugar breakdown products like furfurals, formic acid, hydroxymethylfurfural, and other compounds including tannins, resins, and phenolics. These kinds of waste streams are generated during the biomass pretreatment step. The hydrolysis step in biomass processing leaves a lot of residual biomass that remains undigested and in most cases rich in lignin. Residues are also generated in the fermentation process where the fine particles of undigested biomass and yeast cells form aggregates and are considered as waste. Apparently, the residues rich in lignin may be used to recover lignin, and the pretreatment liquors can be a source for recovery of chemicals and probably as a growth medium for microbes to produce high-value compounds. The chapter describes the concept of waste utilization/valorization in lignocellulosic biorefineries so as to make the biorefinery operation zero or near-zero waste and improve their economies.

Non-conventional Yeast cell factories for sustainable bioprocesses.

The non-conventional yeasts Kluyveromyces lactis, Yarrowia lipolytica, Ogataea polymorpha and Pichia pastoris have been developed as eukaryotic expression hosts because of their desirable growth characteristics, including inhibitor and thermo-tolerance, utilisation of diverse carbon substrates and high amount of extracellular protein secretion. These yeasts already have established in the heterologous production of vaccines, therapeutic proteins, food additives and bio-renewable chemicals, but recent advances in the genetic tool box have the potential to greatly expand and diversify their impact on biotechnology. The diversity of these yeasts includes many strains possessing highly useful, and in some cases even uncommon, metabolic capabilities potentially helpful for the bioprocess industry. This review outlines the recent updates of non-conventional yeast in sustainable bioprocesses.

Enzymes for Bioenergy

Lignocellulosic ethanol is emerging as the prominent candidate for renewable liquid transportation fuels, and the conversion of biomass to ethanol requires enzymatic hydrolysis. Enzymes that hydrolyze biomass have been the subject of several studies, since the cost estimations of second-generation ethanol show significant contributions by this single consumable. The chapter introduces biomass-hydrolyzing enzymes in the context of biorefineries and provides an overview on the current knowledge and understanding of these enzymes with respect to their types, mode of action, regulation of gene expression, and synergies. The changing concepts about the role of individual enzymes and the new discoveries on lignocellulose breakdown are presented to highlight the developments in biomass hydrolysis paradigm. It also covers the current strategies employed for commercial production of different lignocellulose-hydrolyzing enzymes and their blending to derive efficient cocktails. Finally, the importance of cost reduction in production and usage of biomass hydrolysis enzymes for a cost-effective bioethanol technology is discussed along with the current approaches in addressing this.