STUDY ON MICROBIAL ENZYMES DEGRADING LIGNOCELLULOSIC FOOD WASTE AND IN BIOREMEDIATION OF POLLUTANTS

 STUDY ON MICROBIAL ENZYMES DEGRADING LIGNOCELLULOSIC FOOD WASTE AND IN BIOREMEDIATION OF POLLUTANTS

Abstract

The lignocellulosic food waste from agro-industries (sugarcane baggage, apple pomace, rice bran) are discarded or used as fodder. The pomaces and baggage can contain moisture as high as, up to 75%. Added up with high chemical oxygen demand and biological oxygen demand are prone to causing major environmental and health problems.

Microbial enzymes (Trichoderma reesei, Aspergillus niger, Viscozyme L, Celluclast 1.5L, cellobiohydrolases, bacterial amylase, endoglucanases and b-glucosidase) working in synergy can hydrolyse the wastes at a faster rate than traditional methods producing invertase that can be used as industrial sweetener and also as a biofuel or in production of chemicals for biorefineries.

Bioremediation is a technique of using microbial enzymes to recycle wastes or degrade pollutants with the help of biotechnology, such that they can be reused by certain organisms, without causing any environmental damages.

Enzymes such as oxido-reductases and hydrolases have great prospect in remodifying toxic and organic pollutants into useful substances and thus help in sustaining a pollution free environment.

Introduction

Today, Food and Agriculture industry is developing and is advancing at a very rapid pace. Improvement in economic growth has brought about huge and significant investments in this sector. But with the increase in industrialisation of agricultural sector, the amount of waste which is generated have also significantly increased. This has become a challenge from environmental point of view. Certain studies have put forward that around five million metric tons of Industrial waste for Biomass are being produced every year. (1)

Not only this, almost all of the waste which has been generated by agro-based as well as food industries are mostly very high in their nutritive contain and does can be very good breeding grounds for disease causing microbes. Left unprocessed or untreated they can be reason for upcoming epidemics. The microbes can be used to produce certain enzymes that can simplify the technique of waste management. Moreover, microbial enzymes are more work-efficient than plant and animal enzymes. (2) The enzymes found their uses in food, paper and detergent industries. E.g.-Amylolytic enzymes. (3) Apple pomace and sugarcane baggage are enriched with high concentrations of cellulose, pectin, hemicellulose and are lignocellulosic. These can be converted into monomers of sugars and acetic acids. (4,5,6)

Our biosphere is filled with wide variety of microorganism. This is because they are versatile and nutritionally active, which makes their growth inevitable in each and every areas of the earth. Some microorganisms have the ability to utilise toxic pollutants in our own human welfare or the Welfare of environmental conditions. this Process is called bioremediation. (7) By using process of bioremediation, microorganisms can be used for solving dangers caused by many pollutants. They can act as a significant polutent removal tool that could be used in soil, water and also in sediments. Microorganisms used for taking microorganisms itself is a very effective technique and would help us in restoring our natural surroundings and also would help in prevention of further pollution. (8)

Value of Agro-Based Industrial Waste

In the past decade, a number of case studies have been carried out to examine the effective utilisation of Agro Industrial waste and that it can be used as a source of potential raw material to help in manufacture of value-added products. Almost all of these studies have been performed in countries where the economy is dependent on agricultural processes. For example, Brazil being the largest exporter of sugarcane and also the second largest producer of Ethanol in the world. (8) In the current scenario, Ethanol and other liquid fuel production is the only area in which the wastes are being used. But researchers are concerned about certain fermentation techniques which could convert lignocellulosic agricultural wastes into raw materials for production of various enzymes. (9,10).

Wastes from Industries

The use of the indudtrial enzymes can increase by manifold with a Compounded ANNUAL Growth Rate (CAGR) of around 4.7 percent between the years 2016-2021. (11)It is also reported that around half of the cost production is given to capital investment, whereas only one-third of the such cost can be utilized in buying raw materials. Substitution of feedstocks with lignocellulosic components would result in an increased return over investment.

Enzymes acting over Polysaccharides

Alpha Amylase

They belong to a family of enzymes that randomly cleave α-1, 4 linkages between adjacent glucose subunits in polysaccharides, resulting in the release of short chain oligomers and α-limit dextrins. They are extensively used in the production of detergents, bread, beer, paper and in pharmaceuticals. (12)

Cellulase

A combined hydrolysis by three key enzymes: endoglucanase (E.C. 3.2.1.4), exoglucanase or cellobiohydrolase (E.C.3.2.1.176) (E.C.3.2.1.91) and β-glucosidase (E.C.3.2.1.21) results in the depolarisation of cellulose. They help in catalysing the cleavage of glucosidic bonds. (13) They have a major role un the production of bioethanol. (14) Other than this, it is also used in detergent industries, in production of paper, pulp and in textiles. (15) Since it is extensively used, scientists have tried and are still studying the use of vegetable and fruit leftovers to produce the enzymes under solid state fermentation. For example- using banana peels. This could cut down th cost production to many folds. (16)

Pectinase

They help in the process of catalysing the disintegration of pectin-containing compounds. Pectin are avery important constituent of plant cell wall. The enzyme founds its extensive use in fruit juice industries and wine making to clarify and remove turbidity of finished product. (17)

Enzymes acting on Proteins

Protease

These enzymes perform he process of proteolysis by undergoing hydrolysis of peptide bonds that merge amino acids in polypeptide chains. It consistently holds the market share of around 60 percent. (18) Detergent proteases are a major component of its sale. Aspergillus sp. has been a subject of study in the recent years for the production of protease enzyme from lignocellulosic sources or industrial wastes with the help of solid-state culture. (19)

Cellulosomes

They are extracellular in nature and contain carbohydrate binding molecules that help in scaffolding and enable them in formation of various enzyme-substrate complexes. (20) The use of cellulosomes for converting cellulosic materials or components into fermentable sugars is gaining momentum rapidly. 

Several studies were performed for determining the effectiveness of this component and to achieve hydrolysis by cellulosic enzymes. The results were positive and are being experimented over by the European Union. (21)

Principle of Bioremediation

Certain microorganisms possess enzymes that use environmental contaminants as their food. Thus they can be aided for the task of contaminant destruction. The aim is to provide these microorganisms and enzymes with utmost nourishment and nutrients for their metabolism. This will result in degrading or detoxifying hazardous substances for the environment. Enzymes are the sole player in the process of metabolization. They belong to certain groups like- Oxidoreductatses, lyases, Transferases, Isomerases and ligases. To have a complete effect, bio-remedifier must attack on the pollutant and destroy it completely or convert it to non harmful components. (22) The conversion is regarded as harmless when the elements are changes into naturally occurring compounds such as-carbon dioxide, water and inorganic compounds fir for consumption of humans and other animals. (23)

Conclusion

Lignocellulosic food industrial and agro-based wastes are one of the cheapest source and are very easily available in form of simple carbohydrates for carrying out the process of valorisation and subsequent value addition. Bacterial and fungal species can be used simultaneously for production of various enzymes with the help of agricultural wastes. High saccharification rates provided by pre-treatments can ensure enzyme loading at lower levels and can further improve the economics of enzyme production. Solid state fermentation has been very helpful and more productive than the submerged type and should be used extensively for this purpose. Though certain modifications are necessary in the models for increasing the effectiveness and higher yield in the production rates. But with governmental support and help from private sectors evolution is quite certain. The industrial wastes can also provide as a source of carbon which can be used in upscaling fermentation processes.

Bioremediation is one of the best and most effective way of remediating, cleaning, managing and recovering techniques for ending various problems in relation to polluted environment, with the help of microbial activity. The speed of degradation is dependent on the type, quality and quantity of the microbes used for the same. Also, it works in competence with biological agents, inadequate supply with essential nutrients, unsuitable external anaerobic conditions, pH, temperature. In spite, of all these conditions, bioremedifying is the safest process of cleaning up our environment. Since, we are using microbes against microbes and enzymes against enzymes. The advantages of the process are way greater than its disadvantages and is also cheap than the use of other chemical methods.

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