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Research Article

Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida

Pushpa S. Murthy and H.K. Manonmani
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Studies were carried out to cultivate Pleurotus florida on Coffee industry wastes such as Coffee Cherry husk, Coffee parchment husk, Silver skin, Coffee spent wastes, dried leaves with and without supplementation of agricultural wastes such as wheat bran in different combination for cultivation of Mushroom. Other physicochemical parameters were also optimized for maximum mushroom yield. Ten percent spawn rate yielded maximum mushrooms at 50% moisture level. The first fructification occurred after 16 days and 220 g of mushroom were obtained after four flushes per 100 g of the substrate at optimized conditions. The nutrient quality of the mushrooms was on par with the reported values of mushroom cultivated on the other substrates. The Results showed the feasibility of using all the coffee industry wastes such as coffee cherry husk, parchment husk, silver skin, spent waste and also with supplementation of agricultural wastes such as wheat bran for cultivation of edible fungus, employing solid state cultivation/fermentation for bioconversion process. P. florida is a promising mushroom for cultivation in terms of its high productivity, simple means of bioconversion on cheap organic substrates such as coffee industry wastes and a short production cycle compared to many other cultivated mushrooms.

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Pushpa S. Murthy and H.K. Manonmani, 2008. Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida. Research Journal of Environmental Sciences, 2: 145-150.

DOI: 10.3923/rjes.2008.145.150



Coffee is one of the most important agricultural commodities in the world and are cultivated for commercial production. In the coffee industry, only 9.5% of the weight of the fresh material is used for the preparation of the beverage and 90.5% is left as residue. At different stages from harvesting to the consumption coffee processing industries generate several residues such as coffee cherry wastes, coffee parchment wastes, sliver skin, coffee spent grounds, coffee leaves which is discarded with no treatment. It is estimated that more than two million tons of coffee husk and spent grounds and one million ton of the parchment husks are produced annually from the processing units. Although coffee leaves are not considered as residue, fallen leaves in voluminous quantity all round the year pose environmental problems. They also facilitate good environment for pathogens and pests. These residues have not been practically utilized because of their toxic nature i.e., the presence of caffeine, tannin and polyphenols. Therefore their disposal is a major environmental concern (Soccol, 1996).

India is one of the largest producers of coffee in the world (ICO, 2003) and also one of the major agricultural countries accordingly has the largest quantity of the wastes generated from the processing industries and agricultural wastes generated is also enormous. One of the strategies to utilize agro industrial wastes is to grow edible fungi such as Mushrooms that will not only reduce the toxic nature of the wastes but also help in obtaining protein rich food on cheaper substrate. Production of mushrooms using coffee pulp has been tried since 1984, Martinez and Quirarte (1984). However utilization of other coffee industry wastes for mushroom cultivation has been at infancy. Practically very few reports are available on this aspect.

The objective of the study is to explore the possibility of the utilization of the coffee industry wastes such as Coffee parchment husk, Cherry husk, Silver skin, coffee spent wastes and fallen dried leaves for the cultivation of mushroom for human consumption in an economical way.


The Mushroom Pleurotus florida was obtained by Mushroom Development Scheme, Horticultural Development Farm, Kukkarahally, Mysore, India. The isolates were maintained on 1.5% malt agar slants and stored at 4°C.

Sorghum vulgare (Jowar) was obtained from the local market. Coffee industry wastes such as Coffee parchment husk and Coffee cherry husk were obtained from Coffee curing works, Mysore, India. Wheat bran was obtained from ISMT Dept CFRTI, Mysore, Coffee spent waste was obtained from local restaurants. Coffee leaves were picked up from coffee gardens. All the chemicals used in the preparation of media and a regents were of analytical grade purchased from standard companies.

Spawn Preparation
Jowar seed (100 g) was weighed into polypropylene bags and autoclaved at 121°C, 15 lbs for 20 min. Sterile water was added sufficient to keep jowar moist. Five milli meter mycelial disc of 10-day-old Pleurotus florida was inoculated to these Jowar which were fortified with 2% calcium carbonate and the bags were incubated at room temperature for 20 days.

Seed Inoculum Development
Jowar seeds containing 50% moisture were sterilized by autoclaving at 121°C for 45 min. The cooled bags were inoculated with the 10% grain spawn and incubated at room temperature for 4-5 days.

Substrate Preparation
Dried coffee leaves, Coffee cherry husk, Coffee parchment skin, Silver skin and coffee spent ground waste with or without wheat bran were mixed in different permutations and combinations to a final weight of 100 g (Table 1) and autoclaved in polypropylene covers at 121°C for 20 min. They were then cooled to room temperature and 10% sterile distilled water was added to provide required moisture level.

Culturing Conditions (Solid State Fermentation-SSF)
The sterile substrates were inoculated with grain spawn at 10% inoculum level (on wet weight basis) by layering methodology. They were manually mixed, loosely tied and incubated at room temperature in dark until mycelium colonized the substrate. Then the polypropylene bags were opened and were hang on wood rods. The colonized substrates were exposed to air at room temperature (25-27°C). Tap water was sprayed thrice a day on the mycelial substrate. The fruiting bodies were harvested at 7-9 cm in diameter of caps. After four flushes the residue and mushroom were analyzed. The yield was expressed as% Bioconversion Efficiency (BCE), grams fresh mushroom per 100 g dry substrate (Belewu et al., 2005; Rajarathnam et al., 2001).

Table 1: Combinations of the coffee industry wastes
Image for - Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida

Effect of Moisture and Spawn Rate
Substrates were prepared with different moisture levels such as 25, 50 and 75% for culturing of mushrooms by Solid-State Fermentation (SSF). Similarly different spawn rates were tested which included 2, 5, 10 and 20%. After mushrooms flushes were collected both substrate and mushroom were analyzed.

Analytical Method
Protein content in Mushroom and substrate were done by kjeldhal method. The fiber content was determined by acid alkali digestion method, Moisture, total ash and mineral contents were determined according to AOAC (1975). Total reducing sugar was determined by Lane and Eynon method (AOAC, 1975). Caffeine and tannin content were determined according to Leifa et al. (2001). All results are an average of triplicate values.


India is one of the largest producers of coffee, the coffee industry wastes are produced in voluminous quantity and 90% of the coffee industry produce goes as a waste. These wastes, similar to other agro-industrial are rich in organic nature and nutrients (Table 2). The cultivation of mushroom was attempted not only to utilize these wastes for mushroom cultivation which has good nutritional and therapeutical value but also reduce the toxic contents of coffee wastes.

Mushroom Production on Different Coffee Industry Wastes
The coffee industry wastes were used for the cultivation of mushrooms either individually or in combination (Table 1). When these substrates, were used individually, the yield of mushrooms were very low. Coffee dried leaves did not help in the growth of mushrooms. Among individual substrates, highest mushroom yield was observed with coffee cherry waste, followed by coffee spent grounds. Wheat bran individually supported the growth of 70 g of mushrooms. But when the mixture of substrates was used, combination 1 i.e., mixture of all substrates yielded maximum mushroom yield. Two hundred and twenty gram of mushroom were obtained after four flushes in 41 days. Combination 2, where silver skin has been eliminated was next best, with a yield of 190 g of mushrooms/100 g substrate mixture used. The combination 3, which does not contain silver skin and wheat bran, yielded 181 g mushrooms. Combination 4, which does not have, parchment skin, silver skin, helped only the growth of mushrooms with 152% BCE.

Coffee pulp has been used for the cultivation of mushrooms (Martinez et al., 1992; Contreras et al., 2004), other substrates such as cereal straw, sugar cane bagasse, rice straw, grass, corn cob have been used along with coffee pulp (Contreras et al., 2004; Martinez et al., 1992). Coffee husk has been used along with coffee pulp for growth of Lentinus edodes (Leifa et al., 2000). Agricultural wastes such as saw dust, sisal waste and paddy straw supplemented with chicken manure has been used for the cultivation of Oudemansielle tanzanica nom. Prov. (Magingo et al., 2004). Rice straw supplemented with cotton seed powder has been used for the cultivation of Pleurotus florida (Rajarathnam et al., 2001). The coffee industry wastes other than pulp and husk and spent ground have not been tried for the cultivation of mushrooms. Also, the yield of mushroom has been better by using combination of different coffee industry wastes. In our studies the highest BCE of 220% was obtained with combination I. Rajarathnam et al. (2001) have obtained a BCE of 235% with Pleurotus florida culturing on rice straw supplemented with Cotton seed powder.

Effect of Moisture and Spawn Size
The yield of mushroom increased with increase in moisture level till 50% moisture. At 25% moisture level the yield was only 83 g, substrate dipped in boiling water did not help in better yield.

It is reported that in solid-state fermentation, an optimum level of moisture is a crucial factor. Higher moisture levels result in decreased substrate porosity, which in turn prevents oxygen transfer. At the same time low moisture level leads to poor accessibility of nutrients resulting in poor growth (Pandey, 1992a, b).

Spawn size plays a key role in the growth and yield of mushrooms. The yield of mushrooms increased with increase in spawn size up to 10% level. A further increase in spawn size did not help in increased yield of mushroom. The amount of inoculum should be optimum to allow for the ramification of the fungus. At 10% spawn size the fungus ramified the whole substrate within 6-8 days i.e., the mycelial growth was vigorous (visual observation), active and was maximum. Leifa et al. (2001) obtained good mycelial growth and mushroom yield at spawn rate of 10-15%. However, spawn rate of 10% was considered suitable. The spawn rate has also been considered as the principal factor for edible fungus cultivation by SSF. There has been variation in spawn rate with different substrates used. Rajaratnam and Zakia (1987) have reported that the spawn rate of less than 10% facilitated the contamination and decreased the biological efficiency and more than 20% spawn rate has been recommended on paddy straw and paddy straw supplemented with cotton seed powder. However, a 2% spawn rate has been recommended by most other authors for mushroom production on different substrates (Yang, 1986; Fan and Ding, 1990).

Composition of Spent Coffee Industry Residues
Table 2 shows the analysis of the coffee industry residues mixture used for the cultivation of mushroom i.e., combination I before and after mushroom cultivation, the protein, fat and fiber contents of the substrate mixture decreased. The caffeine and the tannin contents also decreased. This indicated that the fungus was able to degrade caffeine and tannins partially. The caffeine and the tannin concentrations decreased by 50 and 41% (data not shown), respectively after fermentation. However there are not much reports about action of Pleurotus sp. on caffeine and tannins in any coffee industry waste used on substrate. Only Fan et al. (1999) have reported 60-69% reduction of caffeine and 79-17% of decrease in tannin contents on coffee husk and spent grounds when grown with P. ostreatus LPB09.

Analysis of the Mushroom
The performance of mushroom on coffee industry wastes is shown in Table 3. Analysis of the mushrooms is shown in Table 4. The fruit body of Pleurotus sp. did not contain caffeine and tannins when grown on coffee industry wastes (data not shown). This indicated that the fruit body did not contain any toxic materials found in coffee industry wastes. But the caffeine and tannin contents in spent waste was reduced indicating degradation of the these toxic materials by mushroom.

Due to the presence of these anti-physiological and anti-nutritional factors in coffee-industry wastes, these waste materials have not been able to be used as feed for cattle and other livestock or substrate for fermentation processes. Thus these substrates remain unutilized or poorly utilized resulting in environmental problems. If these toxic materials could be decreased or removed or degraded to non-toxic compounds by fungal growth, it would open new avenues for their utilization as feed. This will improve its value to be used as substrate for bioprocesses (Fan et al., 2000a, b).

Table 2: Analysis of coffee industry waste before and after mushroom cultivation
Image for - Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida

Table 3: Performance characteristics of P. florida grown on coffee residues
Image for - Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida

Table 4: Nutrient composition of the mushroom grown on coffee industry wastes
Image for - Bioconversion of Coffee Industry Wastes with White Rot Fungus Pleurotus florida

Mushroom cultivation not only reduces the environmental impact of the wastes used as substrate, but also provide an economical acceptable alternative for the production of food of superior taste and quality as well as high value added metabolite such as enzymes or polysaccharides (Israilides and Phlippoussis, 2003; Zervakis and Philippoussis, 2000).

Coffee industry wastes have shown to be good substrate for the cultivation and production of Pleurotus sp. by solid state cultivation through a biotechnological approach which leads to an effective and economical way to utilize this otherwise unused residues and improve the economy of the coffee industry.


The authors are grateful to Head, Food Microbiology and Director, CFTRI, Mysore for providing the necessary facilities to carry out the above research.


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