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According to the Waste Framework Directive (European Directive (WFD) 2006/12/EC), waste is defined as "Any substance or object the holder discards, intends to discard or is required to discard" and it is said further, "Once a substance or object has become waste, it will remain waste until it has been fully recovered and no longer poses a potential threat to the environment or to human health" (1). This means that exploitation of the waste, recovering valuable products form it in such a way that the pollution is minimized is preffered.The Commission also enlist the wastes categories (solid and liquid), including waste from mining industry, textile industry, petro-chemicals industry, agricultural industry, fishing industry, photographic industry, metal industry, plastic industry, and wastes from organic and inorganic chemical processes, municipal and construction waste (2).
In Sweden alone almost 124 Million tonnes of waste was generated in 2006 (Figure 1).121 M ton of this was nonhazardous comprising mineral waste, wood waste and Industry effluent sludge. Half of this was land filled. Two third of the remaining was recycled and one third was used to recover energy. The hazardous waste was mainly from the construction and household sector (3).
Figure 1: Sweden Waste Statistics 2006 (Modified -3)
The land filled solid waste and sludge can be treated to recover the products from them. Most of the waste recovery plants rely on chemical methods but as they need the high energy input, cost and further are a threat to environment and health, there has always been a quest for alternative environment friendly methods. Biotechnology has proved successful in this aspect. The purpose of this report is to discuss the Industrial products that can be obtained from waste industries by using micro organisms and enzymes. However, it's not possible to discuss all the waste industries in detail in such a short report so fish industry waste is chosen to describe in detail.
Fishery Waste-Crustacean shells
Marine biomass in addition to providing food is also the raw source of biopolymers, enzymes and other pharmaceuticals (4). The waste therefore accumulated by Fish industry with no exception is considerable and in large amount depending on the product. Almost 25 % of the total world marine capture fisheries are waste (5). Mostly the fish industry waste comprises of fish offal, processing waste water and byproducts like shells of crustaceans (crabs, lobsters, krill, shrimps and prawns) and shellfish (6, 7). Many bioactive compounds have been reported to be isolated form fish offal, waste water and shells (8- 10).
According to FAO ISSCAAP, 4 424 075 tons of crustaceans were exported in 2006 , which contributes to almost 8.22 % of the total fishery export (11).Crustacean shells a waste of fish industry was disposed off either as land fill or dumped at sea ,but now due to technological developments these wastes can be utilized in a better way. Shells processing was hampered due to their less solubility and biodegradation resistance. (6,7) . Basically, Shells are composed of protein, chitin and calcium (12). Chitin, a linear polymer of N-acetyl-D-glucosamine , is second abundant natural polymer (13) Chitin , its deacetylated derivative chitosan- a hetero polymer of D-glucosamine and N-acetyl glucosamine units and chitosan oligomers, all are bioactive materials and have many potential applications due to their non-toxic biocompatible and biodegradable nature .Table 1 (14,15).
Table 1: Main reported potential applications of Chitin and Chitosan (Modified- 15)
Reduces bean root-rot (Chitin)
Abrasive for skin cleansing
1.Abrasive for skin cleansing,2.Hihg water holding capacity moisturizer
1.Purifies municipal, industrial, food processing effluents,2.Precipitates, recovers proteins,3.Chelates, removes pollutants and recovers microorganisms
1.Clarifying agents, 2.Food preservative
In photographic films
1.In micro porous spray-dried particles for chromatography,2.In membranes for reverse osmosis, ultra filtration
1.Stimulates immune system,2.Inhibits thrombin hydrolytic activity, 3.Controls appetite, prevents gastritis
1.Controls appetite, prevents gastritis, 2.Affects blood coagulation, 3.Facilitates wound healing, reduces blood serum cholesterol, 4.In diet, decreases cholesterol level, 5.Tissue regeneration, vascular surgery
Other Biotechnological applications
1.In preparation of membranes for encapsulation of tissue , bacterial cells and mammalian cells, 2.In cells and cell debris recuperation + for SCP recovery
However their applications in functional food and pharmaceuticals are restricted due to their high viscosity, and low solubility at low pH (16). So Chitosan is further converted into oligomers by chemical or enzymatic methods .These Chitosan oligomers also have been proven to have antimicrobial and antitumor activity in addition to being water soluble (17, 18). The crustacean shell waste is used commercially in the production of chitin, chitosan and their oligomers either by using chemical or biological methods (fig 2) (7).
Figure 2: Schematic diagram for the preparation of Chitin, Chitosan and their oligomers (Modified-7)
1.2 Process of production:
Deproteinisation 3% NaOH, 90Â°C
(1:3 solid: liquor) x 2
Deacetylation 50% NaOH,
(1:10 solid: liquor)
(1.25M HCl; 1:10 solid: liquor)
Ground to paste
Figure 3: Chemical preparation of Chitin and Chitosan from Crustacean Shell waste (Modified -19)
1.2.1 Chemical Method:
Commercially, chitin and chitosan were first produced thermo chemically using grinding, demineralization, deproteinisation and deacetylation steps (19, 20) (fig 3). Two worlds' largest producers in Japan and USA of chitin and chitosan used this technique (6).However the drawbacks of such a chemical method like High chemical disposal, high energy input and lost of other bioactive materials like proteins and pigments are noteworthy (6). The quality of chitosan produced also depends on the condition used in the production process (21, 22). This method thus becomes undesirable and expensive if considering the chemical waste problem (23).So alternative method of using microorganisms and enzymes have been reported (24).
1.2.2 Biotechnological Method:
Biotechnological process can be employed at all the stages of the process.
Shell waste ground to Demineralization Flake:
Lactic acid fermentation has been used as an alternative for the counter chemical step in shrimp waste, crayfish exoskeleton, prawn waste and red crab shell waste (25).Lactobacillus sp. Strain fermentation resulted in the production of lactic acid .This lactic acid which is produced by the breakdown of glucose lowers the pH of the medium which in addition to preventing the medium from spoilage microorganisms also solubilizes the calcium carbonate component of the shell (26). Some times ensilation can also be carried out by addition of extra organic acids (27)
Demineralization Flake to Chitin:
The conventional protein removal step uses NaOH as shown in fig 1. Different microorganisms and proteolytic enzymes have been exploited for this step also (28, 29). Microorganisms studied include Pseudomonas aeruginosa, P. maltohpilia (30) and Bacillus subtilis (29).Lactic acid fermentation is involved in all of these which combine demineralization (as discussed in the above section) and deproteinisation by proteolytic enzymes produced by the added species and also are already in the waste from the gut of the crustaceans (23, 26). A successive chitin production from red crab shell wastes was carried out by using two species in two steps fermentation. The species, Lactobacillus paracasei for demineralization and Serratia marcescens for deproteinisation, results in a co removal of calcium carbonate and proteins (25). The microbial fermentation process depends on the quantity of inoculation, pH, substrate concentration, and fermentation time (31) Lactic acid fermentation results in syrup which is altogether rich in proteins, minerals, asthaxanthin and a solid chitin fraction.
Chitin to Chitosan:
Chitin can be converted enzymatic ally to chitosan.Microrganisms that produces chitin hydrolases are Mucor roxii, (32, 33), Colletotrichum lindemuthanum (34) and Phycomyces blakesleeanus (35), Serratia marcescens (36), Absidia Coerulea (37) and Apergillus nidulans (38).
Chitosan to chitosan oligomers:
Chitosan can be converted into its oligomers by chemical, physical and enzymatic methods. Chemical means uses traditional acid treatment so needed high cost and also gives low yield and residual activity (39). Sonication and electromagnetic radiation can also be used (40). But enzymatic means are preferred because the reaction can be controlled by means of pH, Temperature and reaction time (41). Chitosan hydrolases including lysoszyme ,hemicellulases, lipases, amylases, papain probnase,pectinases and cellulases are used to convert it into its oligomers which are proven to have better characteristics than chitosan as discussed in section 1.1.Some of the Microorganisms that are able to able to produce them are bacteria (42), fungi (43), myxobacteria (44), and actinomycetes (45).
Chitin to Chitin oligomers:
Chitin oligosaccharides have various medical functions such as elicitor action, antitumor activity and role in osteoarthritis treatment (46). Previously theses were produced by acid hydrolysis (47) but being not an environment friendly method, alternative enzymatic method by using chitobioses from Aeromonas sp. are reported (48).
1.3 Market and Economy:
There was inconsiderable research or industrial work done on Chitin until in 1977 the 1st International conference on Chitin-Chitosan (ICCC), in Boston took place, which activated this filed .In this conference, the production cost for chitin as was estimated to be ranging from dollar 1.20 -kg (49) (Chitin) to Dollar 5.53 per kg (50) (Chitosan) excluding the transportation price from the waste site to the processing plant but now the transportation cost is considerable. However Russia developed an electrochemical method for the extraction of chitin from waste which claims to produce better quality chitin by using milder conditions and also the plant can be containerized as it s packed and small making it able to transport to the waste area easily(51,52). the down streaming process needed for the final product achievement really makes them expensive like drying the large water content is one of the limitation and also it depends on the product needed for example the medical grade chitosan costs 25,000 dollar per kg, as this includes the high down streaming process cost and only half a dozen of companies all over the world are producing this quality grade chitosan. (53). so the economy input no matter which method they are using is still high. But still different qualities of Chitin, chitosan and its oligomers are being produced.
The first companies in USA and Japan in 1980 used the general acid treatment methods. With the passage of time diverse applications of chitin came into notice initiating the market also in chitin production. Now chitin and its derivatives are produced mostly chemically but some companies are using chemo enzymatic treatment for their production .China is the top producer of chitin, producing almost 80 % of the whole chitin. Other producers are Malaysia, Indonesia, Canada, Germany and few other countries. It is estimated that the worldwide production of chitin and its derivatives from waste is almost 37 300 metric tons (54).However one pilot plant is being working on Biological production of Chitin from Crustacean shell waste based on Lactic acid fermentation in UK. A company named Carpacics NI Ltd., (2000) has licensed the technology by Queen's University Belfast Chemistry department to a fish processor Kilkeel, Co. Down, which is involved in producing 30 tonnes of waste in a 500 liter bioreactor per week (55).
1.4 Future potential
No doubt biological method is the best way to degrade the fishery waste and produce and chitin but still there are some hindrances and research is needed to in the following areas to finally have a Commercial biological Chitin production plant.
Biological treatment requires almost 7 days for one process. Time reduction needed which will of course reduce the operating cost.
Chemical treatment even after enzymatic deproteinisation as calcium carbonate and proteins remain sometime after that, so research needed to decrease the dependency on chemical method.
Enzymatic deacetylation of chitin needed the water soluble chitin, research on using insoluble chitin.
Biotechnological processes no doubt offer a great potential for isolation of valuable products from the waste materials using environment friendly and economic methods as compared to the harsh chemical methods in use, which are a continuous threat to health and environment. There is a need for more research in this field which can make this process run on large industrial scale.