Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based composts and locally available casing materials Part III : Dry matter , protein , and carbohydrate contents of Agaricus bisporus

This study was performed to determine the effects of composts and casing materials on dry matter, protein, and carbohydrate contents of the fruit bodies of Agaricus bisporus. Results showed that Agaricus bisporus cultivated on group I and group II casing soil groups showed remarkably higher dry matter and carbohydrate contents compared to other casing groups. No significant differences were found among casing soil groups in terms of protein content of Agaricus bisporus cultivated on wheat straw. But, there were significant differences between casing soil groups in terms of protein content of Agaricus bisporus cultivated on waste tea leaves.


INTRODUCTION
Cultivation of edible mushrooms with agricultural residues, such as rice and wheat straw, is a value-added process to convert these materials, which are otherwise considered to be wastes, into human food (Zhang et al., 2002).Since ancient times mushrooms have been consumed by humans not only as a part of the normal diet but also as a delicacy because they have highly desirable taste and aroma (Kurbanoglu and Algur, 2002).
More than 2000 species of mushrooms exist in nature but only approximately 22 species are intensively cultivated, for commercial purposes, on ground or wood and utilizing particular environmental and nutritional conditions (Manzi et al., 2001).Fruit bodies of mushrooms are appreciated, not only for texture and flavor but also for their chemical and nutritional characteristics (Manzi et al., *Corresponding author.E-mail: memetcolak@yahoo.co.uk or cmehmet@mu.edu.tr.Tel: +90-252-2111715;Fax: +90-252-2238511. 1999).In most countries, there is a well-established consumer acceptance for cultivated mushrooms (A.bisporus, Pleurotus spp., Lentinus edodes, Volvariella volvacea, Auricularia spp.etc.) (Diez and Alvarez, 2001).In this study, it was aimed to determine nutritional values such as, dry matter, protein, and carbohydrate contents of A. bisporus cultivated on wheat straw and waste tea leaves based composts and using some casing materials.

Preparation of compost
Two compost based wheat straw and waste tea leaves using wheat bran, ammonium nitrate, urea, molasses, and gypsum as activator materials were prepared.Percentage nitrogen (N) content of the composts were arranged to 2.5%.Composts used in this study are given in Table 1.The composting of substrates were processed using method of Shandilya (1982).The total outdoor composting process (Phase I) took 28 and 35 days for wheat straw and waste tea leaves based composts, respectively.The phase II was pro-

Casing soil
Locally available casing materials such as Peat of Bolu (PB), peat of Agacbasi (PA), and peat of Caykara (PC) were used as peats.Peat of Bolu, peat of Agacbasi, and peat of Caykara were supplied, from Bolu district, Agacbasi district (Surmene-Trabzon), and Caykara district (Trabzon), in Turkey, respectively.Also, Forest soil (FS) was used as casing material, supplied from Meryemana-Trabzon district, in Turkey.Also, we used some secondarily casing materials such as perlite (P), sand (S) and piece of mosaic (PM) with mixture of peat (20:80; v: v) in volume.

Mushroom cultivation
Composts were spawned with 30 g mycelium (Type Horst U1) per kg then filled into plastic bags as 7 kg wet weight basis.During spawn run the temperature of the inlet air is automatically regulated by a cooling surface in the recirculation canal such that the compost temperature is maintained at 24 -25 o C with a minimum supply of fresh air.Spawning room arranged to 25 o C temperature, and 90% relative humidity without ventilation (Hayes and Shandilya, 1977).
After 18 days of mycelia growth, a 3 cm layer casing material covered over the compost.Before casing, chalk was added to give a pH of 7.5 -8.After 7 days, the temperature was lowered to 16 o C, with ventilation, for pinhead production.Watering after casing was done as suggested for commercial growth (Randle, 1984;Shandilya, 1986).

Dry matter content
Fruit bodies of A. bisporus were dried at 100 o C to constant weight to determine their dry matter content.

Protein content
The protein content of fruit bodies of A. bisporus was estimated from the nitrogen content (N x 6.25) as determined micro-Kjeldahl method.

Carbohydrate content
In this study carbohydrates were determined by theorical method using following equation: x 100

Evaluation of test results
Test results were evaluated by a computerized statistical program composed of analysis of variance and following Duncan tests at the 95% confidence level.Statistical evaluations were made on homogeneity groups (HG), of which different letters reflected statistical significance.

RESULTS AND DISCUSSION
Table 2 shows dry matter, protein, and carbohydrate contents of A. bisporus cultivated on wheat straw based compost and using different casing materials.Dry matter values range from 7.90 to 11.36 %, confirming high moisture content of mushrooms (Breene, 1990).This variability is exclusively dependent on the mushroom species since other interfering parameters such as postharvest period, temperature, relative humidity during growth (Bono and Rajatham, 1988).While the highest dry matter (11.36%) was obtained with PB, mixture of PC+P (80:20; v/v) gave the lowest dry matter content (7.90%).
In casing soil groups, group I gave the highest dry matter, but there were no significant differences between group I and group II in terms of dry matter.Dry matter content of A. bisporus group I and group II casing materials was significantly higher than those of other casing groups.Protein values vary 19.13 to 23.06 %.While peat of Bolu gave the highest protein content, the lowest protein content was obtained with mixture of PB+PA.Protein content of A. bisporus cultivated on all casing groups was not significantly different from each other.Carbohydrate varied from 3.05 to 5.38%.While the highest carbohydrate was obtained with PB, the lowest carbohydrate was obtained with mixture of PB+S.No significant differences were found in carbohydrate content of fruit bodies cultivated on group I and group II casing materials.
Dry matter, protein, and carbohydrate contents of A. bisporus cultivated on waste tea leaves based compost and using some casing materials are given in Table 3.
Dry matter values range from 7.74 to 11.46%.While, mixture of PA+PC gave the highest dry matter, mixture of FS+S gave the lowest dry matter.In casing soil groups, group II gave the highest dry matter.Protein values varied from 19.63 to 26.94 %.While the highest protein content was obtained with mixture of PB+PC, the lowest protein content was obtained with mixture of PA+S (80:20; v/v).In casing soil groups, group I and group V gave the highest protein content followed by group II and group VI, respectively.But, no significant differences were found in protein content of A. bisporus cultivated on these groups.Carbohydrate content of A. bisporus varied from 2.88 to 5.70%.Yildiz et al. (2005) found that protein content was changeable according to growth region and structure of species.Diez andAlvarez (2001), andYildiz et al. (1998) reported that the C/N ratio of a grown region affects protein in mushrooms.Co kuner and Özdemir (1997) reported that the protein and carbohydrates levels of mushroom samples are within the range of 19 -35% and  (1997) for dry matter and protein content of mushroom samples (A.bisporus).Han (1999) studied dry matter and protein content of A. bisporus cultivated on a mixture of horse manure, straw, chicken manure, gypsum, and water.He found that dry matter and protein contents of A. bisporus were 7.19 to 9.14% and 32.92 to 34.08%, respectively.Dry matter values in our study are consistent with the values in Han's (1999).But, protein values in our study were lower than Han's findings.It may be due to the differences in the region where mushrooms grown (Yildiz et al. 2005), C/N ratio of a grown region (Diez and Alvarez, 2001;Yildiz et al., 1998), different casing materials used for cultivation of A. bisporus (Baysal, 1999).

Conclusion
This study was designed to determine dry matter, protein, and carbohydrate contents of A. bisporus, cultivated on wheat straw and waste tea leaves based composts and using different casing materials.Dry matter and carbohydrate contents of A. bisporus cultivated on group I and group II casing materials were higher than those of other casing groups.Protein content of A. bisporus cultivated on wheat straw and using different casing materials was not significantly different from each other.

Table 1 .
Wheat straw and waste tea leaves based composts.

Table 2 .
Dry matter, protein, and carbohydrate contents of A. bisporus cultivated on wheat straw based compost.
ab Small letters given as superscript over dry matter, protein, and carbohydrate values represent homogenity groups obtained by statistical analysis with similar letters reflecting statistical insignificance at the 95% confidence level.a In volume.b Each reading is average of five test samples.c Standard deviation.

Table 3 .
Dry matter, protein, and carbohydrate contents of A. bisporus cultivated on waste tea leaves.-8.1% respectively, of the dry weight basis.Our results agree with those reported by Co kuner and Özdemir hıj Note: Small letters given as superscript over dry matter, protein, and carbohydrate values represent homogenity groups obtained by statistical analysis with similar letters reflecting statistical insignificance at the 95% confidence level.aIn volume.bEach reading is average of five test samples.cStandard deviation.4