Category Archives: Composting


Chitinase (EC – the enzyme needed to catalyse the breakdown of chitin which forms a key structural component of many living organisms,  is highly valuable in the waste processing world. Chitin is found in a diverse range of organisms – fungi, bacteria, insects, crustaceans and plants (Ajit et al., 2006; Song et al., 2012). It must be regularly degraded and resynthesized for such organisms to persist.  Marine and soil bacteria rely especially on chitinases to replenish sources of saccharides for further bodybuilding (Orikoshi et al., 2005).

Photo by James Barker. Courtesy of
Photo by James Barker. Courtesy of

My recent post about processing shrimp waste did not do justice to the role chitinases play, but they are a critical component in generating silage and valuable products from such waste (Wang et al., 2006). Part of this process relies on soil borne bacteria and fungi, using chitinases, to degrade the chitin in this waste and return both carbon and nitrogen to the food chain. It has long been realised that such organisms are an integral part of the ecosystem especially these carbon and nitrogen cycles (Cohen-Kupiec and Chet, 1998).   

The chitinase genes have been extensively studied and cloned from different bacteria (Shekhar et al., 2006; Song et al., 2012). They make ideal candidates for industrial applications.  Bacterial chitinases are divided into 3 groups, denoted A, B, and C, which is based on the similarities of their amino acid sequences in the C-terminal catalytic domain (Suzuki et al., 1999). Chitinases have a size range of approximately 20 to 60 kDa but are typically smaller than their plant (25 to 40 kDa) and insect counterparts (40 to 85 kDa). They have a wide stability range, accommodating temperatures from 25 to 80 °C and pH 4.5 to 10.

The most prominent industrial application has been in agriculture (Jung et al., 2003) and pharmacology. Chitinases from the Actinomycetes inhibit the growth of phytopathogenic fungi  by disrupting their cell wall synthesis and have been successfully used in protecting rice, soya and cotton. Transgenic technologies that include the expression of bacterial chitinase genes into cereal crops have provided success in resistance to common phytopathogenic fungal species (Barboza-Corona et al., 2003). The biotechnological applications of Bacillus thuringiensis for the control of pests and fungi have been richly explored with the engineering of heterologous chitinase genes from a number of bacterial resources (Ramirez-Reyes et al., 2004). Bacterial /viral chitinases also have an inherent property exploited in biotechnology, of dissolving the chitin-containing cell wall (Barboza-Corona et al., 2003; Oh et al., 2013), and thus accelerating  protoplast generation. This has led to the development of economically important strains for bio-engineering (Shimosaka et al., 2001). Pharmaceuticals based on chitobiose and N-acetyl d-glucosamine produced by bacterial chitinases have also been generated. (Felse and Panda 2000).

Ajit, N.S., Verma, R., Shanmugam, V. (2006) Extracellular chitinases of fluorescent pseudomonads antifungal to Fusarium oxysporum f. sp. dianthi causing carnation wilt. Curr. Microbiol. 52  pp. 310–6.
Barboza-Corona, J.E., Nieto-Mazzocco, E., Velázquez-Robledo, R., Salcedo-Hernández, R., Bautista, M., Jiménez, B., Ibarra, J.E. (2003) Cloning, sequencing, and expression of the chitinase gene chiA74 from Bacillus thuringiensis. Appl Environ Microbiol  69 pp. 1023–9.
Cohen-Kupiec, R., Chet, I. (1998) The molecular biology of chitin digestion. Curr. Opin. Biotechnol. 9 pp.270–7.
Felse, P.A., Panda, T. (2000) Production of microbial chitinases—a revisit. Biopro. Engr. 23 pp.127–34.
Jung, W.J., An, K.N., Jin, Y.L., Park, R.D., Lim, K.T., Kim, K.Y., Kim, T.H. (2003) Biological control of damping-off caused by Rhizoctonia solani using chitinase-producing Paenibacillus illinoisensis KJA-424. Soil Biol Biochem 35  pp. 1261–4.
Oh, S., Kim, D.H., Patnaik, B.B., Jo, Y.H., Noh, M.Y., Lee, H.J., Lee, K.H., Yoon, K.H., Kim, W.J., Noh, J.Y., Jeong, H.C., Lee, Y.S., Zhang, C.X., Song, Y.S., Jung, W.J., Ko, K,, Han. Y,S. (2013) Molecular and immunohistochemical characterization of the chitinase genes from Pieris rapae granulovirus. Arch. Virol. 158 pp. 1701–18.
Orikoshi, H., Nakayama, S., Miyamoto, K., Hanato, C., Yasuda, M., Inamori, Y., Tsujibo, H. (2005) Roles of four chitinases (chia, chib, chic, and chid) in the chitin degradation system of marine bacterium Alteromonas sp. strain O-7. Appl Environ Microbiol  71  pp. 1811–5.
Ramirez-Reyes, A., Escudero-Abarca, B.I., Aguillar-Uscanga, G., Hayward-Jones, P.M., Barboza-Corona, J.E. (2004) Antifungal activity of Bacillus thuringiensis chitinases and its potential for the biocontrol of phytopathogenic fungi in soybean seeds. J. Food Sci. 69 pp. 131–4.
Shekhar N, Bhattacharya D, Kumar D, Gupta RK. 2006. Biocontrol of wood-rotting fungi withStreptomyces violaceusniger XL-2. Can J Microbiol 52 pp. 805–8.
Shimoasaka, M., Fukumori, Y., Narita, T., Zhang, X.Y., Kodaira, R., Nogawa, M., Okazaki, M. (2001) The bacterium Burkholderia gladioli strain CHB101 produces two different kinds of chitinases belonging to families 18 and 19 of the glycosyl hydrolases. J. Biosci. Bioengr. 91 pp. 103–5.
Song, Y.S., Seo, D.J., Kim, K.Y., Park, R.D., Jung, W.J. (2012) Expression patterns of chitinase produced from Paenibacillus chitinolyticus with different culture media. Carbohydr. Polym. 90 pp. 1187–92.
Suzuki, K., Taiyoji, M., Sugawara, N., Nikaidou, N., Henrissat. B., Watanabe. T. (1999) The third chitinase gene (chiC) of Serratia marcescens 2170 and its relationship of its product to other bacterial chitinases. Biochem J. 343 pp. 587–96.
Wang, S.L., Lin, T.Y., Yen, Y.H., Liao, H.F., Chen, Y.J. (2006) Bioconversion of shellfish chitin wastes for the production of Bacillus subtilis W-118 chitinase. Carbohydr Res 341 pp. 2507–15.

Cellulases in Composting And Fermentation

One of the difficulties in home composting has been the breakdown of woody or cellulosic materials without resorting to burning it. Industrially, there is considerable effort being expended to research processes which will generate useful materials from cellulose, most notably biofuels to replace fossil fuel and intermediates for further processing. Photosynthesis is estimated to produce about 150 billion tons of dry plant material of which half is cellulose (Person et al., 1989). Of that amount, it is known that wheat straw amounts to 150 million tonnes per year in Europe (FAO, 2004).

A key group of enzymes, the cellulases can enzymatically hydrolyse cellulose to generate cellubiose which is then converted to glucose. There are some highly useful reviews covering this subject, the enzymes themselves (Gilbert and Hazlewood, 1993; Bhat, 2000), their production by moulds and fungi using fermentation (Mandels and Weber, 1969) and the strides made to engineer new cellulose enzymes and identify the gaps of which there are many in developing the process further (Bayer et al., 2007; Wilson, 2009).

Cellulase appears to be regarded as a complex made up of hydrolases, β-glucosidases and glucanases which all work synergistically to breakdown wood effectively. This enzyme complex is produced by a range of fungi and bacteria. Cellulose is the major component of cell walls and forms rigid microfibrils which in turn are made up of many dozen linear chains all oriented in parallel. The chains are made up of 1→4 β-linked D-glucose units. The microfibrils are themselves buried in a hemicellulose and lignin matrix. The enzyme complex must work on this mix. Hemicellulose itself is composed of xyloglucans (Type I in primary cell walls) or glucuronoarabinoxlans (Type II in primary cell walls) which in turn are hydrolysed by xyloglucanases and arabinases respectively. In terms of enzyme structure, the cellulases have a common basic structure with a catalytic domain linked to a cellulose binding domain by a glycosylated Pro-Thr-Ser-rich peptide (Gilkes et al., 1991).

When composting the home-user is reliant on exploiting these cellulase producing moulds to breakdown as much of the cellulose as is feasible. Providing a semi-moist, nitrogen balanced environment is crucial hence the disposal of non-wood food waste to provide other nutrients for these fungi to live on.

Bayer, E.A., Lamed, R., Himmel, M.E. (2007) The potential of cellulases and cellulosomes for cellulosic waste management. Curr. Opin. Biotechnol., 18 pp. 237-245
Bhat, M.K. (2000) Cellulases and related enzymes in biotechnology. Biotechnol. Adv. 18(5) pp. 355-383
FAO. (2004) Statistical yearbook production. Food and Agriculture Organization of the United Nations, Rome.
Gilbert, H.J.; Hazlewood, G.P. (1993) Bacterial cellulases and xylanases. J. Gen. Microbiol., 139 pp. 187-194
Gilkes, N. R., Henrissat, B., Kilburn, D.G., Miller, R.C., Jr., Warren, R. A. (1991) Domains in microbial beta-1, 4-glycanases: sequence conservation, function, and enzyme families.  Microbiol Rev. 55 pp. 303–315
Mandels, M., Weber, J. (1969) The Production Of Cellulases. In: Cellulases and Their Applications. ACS Adv. In Chemistry. Vol. 95 Chapt. 23 pp. 391-414
Persson, I., F. Tjerneld and B. Hahn-Hägerdahl, (1991) Fungal cellulolytic enzyme production part of: Persson, I. Production and utilization of cellulolytic enzymes in aqueous two-phase systems. Thesis University of Lund, Sweden.
Wilson, D.B. (2009) Cellulases and biofuels. Curr. Opin. Biotechnol. 20(3) pp. 295-299

Solid State Fermentation

Home composting which I ‘posted’ on briefly earlier, is a form of solid-state fermentation (SSF) whereby the substrate is moist enough to support the growth of micro-organisms without the visible appearance of water between the particles. The technology is generally much more controlled than in home composting which is very much unstructured at the whim of the gardener. The process of SSF has been widely applied for both the small-scale study (Hölker et al., 2004) and large-scale manufacture of food materials such as koji in Japan, for drugs, antibiotics like penicillin (Barrios-Gonzales et al., 1988) and other intermediates for further manufacturing. One of the most useful has been the production of enzymes (Singh et al., 2008). There are some very comprehensive reviews covering its application (Couto and Sanromán, 2006; Pandey et al., 2008).

The benefits are generally a high productivity rate with minimal technological sophistication which keeps further processing costs much lower than a liquid fermentation system. The other benefits also mean being to use certain physiological states for micro-organisms not available elsewhere. Water is also limited and a high product concentration is possible. Enzyme production looks a viable proposition, especially in the production of pectinases from fruit and cellulases for either breaking down lignin or generating bioethanol. Developing the theme further, I’m looking at ways to use food waste as a substrate source and this process offers some potential. Anybody interested in developing the ideas further ?

Barrios-Gonzales, J., Tomasini, A., Viniegra-Gonzalez, G. and Lopez, L. (1988). (Eds.) Penicillin production by solid-state fermentation in bioconversion of Agro-industrial Raw Materials. Raimbault M. Orsrtom, Montpellier Fr. Pp. 39-51.

Couto S, R., Sanroman MA. (2006) Application of solid-state fermentation to food industry a review: J Food Eng. 76 pp. 291–302.

Hölker, U., Höfer, M., & Lenz, J. (2004). Biotechnology advantages of laboratory-scale solid-state fermentation with fungi. Appl. Microb. Biotechnol., 64, pp. 175–186.

Pandey, A., Soccol, C.R., Larroche, C. (Eds.) (2008) Current Developments in Solid-State Fermentation. Springer

Singh, S.K., Sczakas, G., Soccol, C.R., Pandey, A. (2008) Production of enzymes by solid-state fermentation. In: Current Developments in Solid-State Fermentation. Part 2 Springer pp. 183-204

Home Composting

The effective handling of food wastes at home can prove tricky especially if one is hoping to be responsible by returning nutrients to the soil and improving upon vegetable and fruit production. Landfilling is becoming less attractive globally and is slowly being banned in many countries. In 1999, the EU Landfill Directive (Council of European Union, 1999), requested member states would promote recovery and recycling at both the municipal and domestic level as well as reduce their landfill. Much of the organic waste generated is now passed to municipal treatment facilities.

Composting is another form of solid-state fermentation which relies on microorganisms digesting residual waste, raising the temperature to a point where pathogenic organisms are killed in the process. It also produces a reusable organic substrate, a soil conditioner in some instances for returning to the land and in my household is a valuable resource for further growing of food. There are many scientific articles worth exploring on the ‘art’ or the industry of composting (Haug, 1993; Hoitink and Keener, 1993). The approach of LCA –Life Cycle Assessment has been applied to municipal composting (Guereca et al., 2006) in Spain and I refer to the technique in a preceding post. At the smaller scale, the technique has only recently been applied (Colón et al., 2010) with any success. One recent report suggests that 20% of organic houselhold waste (OHW) might be composted at home, based on a study of composting in West London (Smith and Jasim, 2009). Generally, meat and fish is to be avoided to minimise rat infestation but fats, oils and greases might be composted at home if flies are not considered an issue. Fruit wastes can degrade too rapidly to produce an acidic leachate or waste which might need tempering with other materials to reduce taints and smell (Chanakya et al., 2007). The heat attracts slow-worm which I have been lucky enough to keep without sticking my fork into when I turn the heap monthly.

The study by Colón et al., (2010) looked at the composting of just raw fruit and vegetables in an experimental system. They produced a high organic material with a good nitrogen content. They monitored greenhouse gas emissions such as methane, nitrous oxide, ammonia, and volatile organic compounds (VOCs) with the latter measuring 0.32 kg VOC/Mg raw fruits and veg. Methane (CH4)and nitrous oxide (N2O) are notorius for their global warming potential (GWP). These have been calculated to be 25 and 298 over a 100 year time frame respectively according to Solomon et al., 2007. This aspect of home composting was investigated further  by Andersen et al., (2010).

One criterion for Colón et al., (2010)- the eradication of pathogens and other phytotoxic compounds was achieved. Composting itself might contribute to ozone layer and abiotic depletion based on these measures. The authors also used a garden chipper which had an electricity demand and might contribute to acidification using a life cycle assessment. I’d welcome any further thoughts on the process, especially with regards to the use of a macerator for creating a suitable organic waste which might then be used for further processing by composting and the quality of this material.

Andersen, J.K., Boldrin, A., Christensen, T.H., Scheutz, C. (2010) Greenhouse gas emissions from home composting of organic household waste. Waste Manag., 30(12) pp. 2475-2482
Chanakya, H.N., Ramachandra, T.V., Guruprasad, M., Devi, V. (2007) Micro-Treatment options for components of organic fraction of MSW in residential areas. Environ. Monit. Assoc. 135 pp. 129-139
Colón, J., Martinez-Blanco, J., Gabarrell, X., Artola, A., Sanchez, A., Rieradevali, J. Font, X. (2010) Environmental assessment of home composting. Res. Cons. Recycl. 54(11) pp. 893-904
Güereca, L.P., Gasso, S., Baldasano, J.M., Jimenez-Guerrero, P. (2006) Life cycle assessment of two biowaste management systems for Barcelona, Spain. Res., Cons., Recycling 49 pp. 32-48
Haug, R. (1993) The Practical handbook Of Compost Engineering. Lewis Publishers, Boca Raton.
Hoitink, H.A.J., Keener, H.M. (1993) Science And Engineering Of Composting: Design, Environmental, Microbiological And Utilization Aspects. Renaissance Publ., Worthington.
Smith, S.R., Jasim, S. (2009) Small-scale home composting of biodegradeable household waste: overview of key results from a 3-year research programme in West London. Waste Manag. Res., 27 pp. 941-950
Solomon, S., Qin, D., Manning, M., Alley, R.B. et al., (2007) technical Summary In: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., Miller, H.L. (eds.) Climate Change 2007: The Physical Science Basis. Contribution of working group I to the fourth assessment resport of the intergogernmental panel on climate change. Cambridge Univ. Press, Cambridge. UK and New York. NY. USA.

Life Cycle Assessment For Managing Food Waste

Recent investigations into food waste management following my studies in environmental management have led me to look more closely at the life cycle assessment (LCA) approach.

A Rubbish Tip. Photo by hinnamsaisuy, courtesy of
A Rubbish Tip. Photo by hinnamsaisuy, courtesy of

It is a systematic method or tool applied to assess the environmental impact of products, processes or any activity throughout its lifecycle. It has been applied to the management of household food waste, from the extraction of raw materials to prepare the food product through production and the end use and disposal of the waste. An inventory analysis describes all relevant inputs, outputs and the transformation with a review of impact on environment and interpretation of results versus objectives a set out by the Inter. Organisation for Standardization (2006). Generally, LCA is not enough on its own to identify the best options but it promotes networking amongst interested parties such as stakeholders, consumers and service providers, and provision of data which is not always forthcoming (Roy et al., 2009).

A study centred on Sydney, Australia (2005) by Lundie and Peters assessed an ‘in-sink’ food waste processor (FWP) with landfilling, and composting at home or in a communal and municipal waste (codisposal) system. The environmental assessment found that composting when managed properly was the least impactful on the environment. When fully aerated (aerobic), composting does not contribute methane gas into the atmosphere until the system is allowed to operate in an oxygen poor environment (anaerobically). Municipal or codisposal composting improves upon the environmental process further by integrating waste disposal although scale-up leads to intensive transportation to a central site, can produce leachates which are eutrophic and generate larger volumes of methane.

The approach is also suitable for application when options for waste disposal are removed such as land fill as in South Korea (Lee et al., 2007) or severely curtailed as is happening in the United Kingdom. I’d be interested to hear from others on the extent of LCA application in waste management.

International Organisation for Standardisation (2006) ISO 14040. Environmental management Life Cycle Assessment – principles and framework. Geneva.
Lee, S-H., Choi, K-I., Osako, M., Dong, J-I. (2007) Evaluation of environmental burdens caused by changes of food waste management systems in Seoul, Korea. Sci Total Environ. 387 (1-3) pp. 42-53
Lundie, S.; Peters, G.M. (2005) Life cycle assessment of food waste management options. J. Cleaner Production 13(3) pp. 275-286
Roy, P., Nei, D.,Orikasa, T., Xu, Q., Okadome, H., Nakamura, N., Shiina, T. (2009) A review of life cycle assessment (LCA) on some food products. J. Food Eng., 90(1) pp. 1-10

What To Do With Waste Coffee Beans ?

At a recent conference on managing waste fruit materials, a supplier commented on research efforts directed to using waste coffee beans. One of the issues for the coffee processing industry is the increasing amount of sub-standard coffee beans, be they immature, damaged or judged unsuitable for further processing such as roasting. Could sub-standard coffee beans provide a source of antioxidants as well as caffeine and some important diterpenes, and were there any other uses for spent grounds for example ?

Photo by Stuart Miles. Courtesy of
Photo by Stuart Miles. Courtesy of

Coffee antioxidants are well researched, and the majority are chlorogenic acids which makes the beverage, one of the highest known for such components . Roasting mainly destroys the antioxidant potential by reducing the chlorogenic acid potential (del Castillo et al., 2002) so keeping the waste beans as ‘green’ coffee should ensure no further losses prior to extraction. There is some evidence that unless coffee consumption is moderate, it is associated with increases in a number of risk factors associated with cardiovascular disease. For example, raised blood pressure and an increase in total plasma homocysteine levels (Higdon and Frei, 2006). The mechanisms are currently being worked out. On the other hand, coffee consumption may reduce insulin resistance which implies a reduction in the incidence of type 2 diabetes and in inflammation markers (Lopez-Garcia et al., 2006; van Dam et al., 2006). It is worth accessing the web-site for a wealth of articles on the subject because individual or groups of factors in the componentry of coffee beans might be usefully exploited or at least avoided where issues are identified.

Production of industrially useful materials from wastes using environmentally friendly processes is an ideal way to make use of unused or spent coffee beans. The coffee beans and their grounds have been used for the production of activated carbon using steam activation (Nakagawa et al., 2001; Boonamnuayvitaya et al., 2004a) which have subsequently been tested for the adsorption of heavy metals, formaldehyde (Boonamnuayvitaya et al., 2004b, 2005; Kaikake et al., 2007), phenols (Nakagawa et al., 2004), industrial dyes such as malachite green (Baek et al., 2010) and as carbon electrodes in capacitors (Rufford et al., 2008, 2009).

This post scratches the surface on the benefits of using waste green coffee beans and provides only a snap shot on the subject, I’m aiming to maintain a series of posts looking at how waste food materials are being used. When I started writing this post, it was apparent that a large body of evidence is being accumulated on its benefits and each nutritional state deserves appropriate coverage. This element I also hope to address in the future.

Baek, M.-H., Ijagbemi, C.O., O, S.-J., Kim, D.-S. (2010) Removal of Malachite Green from aqueous solution using degreased coffee bean. J. Hazardous Materials 176 pp. 820-828
Boonamnuayvitaya, V., Chaiya, C., Tanthanpanichakoon, W., 2004a. The preparation and characterization of activated carbon from coffee residue. J. Chem. Eng. Japan. 37, pp. 1504–1512.
Boonamnuayvitaya, V., Chaiya, C., Tanthapanichakoon, W., Jarudilokkul, 2004b. Removal of heavy metals by adsorbent prepared from pyrolyzed coffee residues and clay. Separation and Purification Technology 42, pp. 11–22.
Boonamnvayvitaya, V., Sae-Ung, S., Tanthapanichakoon, W., 2005. Preparation of activated carbons from coffee residue for the adsorption of formaldehyde. Separation and Purification Technology 42, pp. 159–168.
del Castillo MD, Ames JM, Gordon MH.(2002) Effect of roasting on the antioxidant activity of coffee brews. J. Agric Food Chem. 50 pp. 3698-3703.
Higdon, J.V., Frei, B. (2006) Coffee and health: A review of recent human research. Crit. Rev. Food Sci. Nutr. 46, pp. 101-123
Kaikake,K., Hoaki, K., Sunada, H., Dhakal, R.P., Baba, Y. (2007) Removal characteristics of metal ions using degreased coffee beans: adsorption equilibrium of cadmium(II). Bioresour. Technol. 98 pp. 2787–2791.
Lopez-Garcia, E., van Dam, R.M., Qi, L., Hu, F.B. (2006) Coffee consumption and markers of inflammation and endothelial dysfunction in healthy and diabetic women. Am. J. Clin. Nutr. 84 pp. 888–893
Nabais, J. M. V., Nunes, P., Carrott, P. J. M., Ribeiro-Carrott, M. M. L., Macías-García, A., Díaz-Díez, M. A. (2008) Production of Activated Carbons from Coffee Endocarp by CO2 and Steam Activation. Fuel Process. Technol. 89, pp. 262.
Nakagawa, K., Fuke, A., Tamon, H., Suzuki, T., Nagano, S. (2001) Preparation of activated carbons from waste coffee beans. Jpn. J. Food Eng. 2, pp. 141–6.
Nakagawa, K., Namba, A., Mukai, S.R., Tamon, H., Ariyadejwanich, P., Tanthapanichakoon, W. (2004) Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes. Water Res. 38 pp. 1791–8.
Olthof, M.R., Hollman, P.C.H., Zock, P., Katan, M.B. (2001). Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humans. Am. J. Clin. Nutr. 73, pp. 532 – 538.
Rufford, T.E., Hulicova-Jurcakova, D., Zhu, Z., Lu, G.Q. (2008) Nanoporous carbon electrode from waste coffee beans for high performance supercapacitors. Electrochem. Commun. 10(10) pp. 1594 – 1597.
_____________________________, Fiset, E., Zhu, Z. Lu, G.Q. (2009) Double-Layer capacitance Of waste coffee ground activated carbons in an organic electrolyte. Electrochem. Commun. 11(5) pp. 974-977
van Dam RM, Willett WC, Manson JE, Hu FB (2006) Coffee, caffeine, and risk of type 2 diabetes: a prospective cohort study in younger and middle-aged U.S. women. Diabetes Care 29 pp.398–403