Effect of different nutritional supplements on the productivity and quality of oyster mushroom (Pleurotus ostreatus)

INTRODUCTION

Mushroom species are fruiting bodies of fungi. They are classified in Kingdom of Fungi, which is also called Kingdom of Mycetae (Ammirati and Seidl, 2007). The use of mushroom as food is an old age practice and there was cultivation record in 60 A.D. (Chang and Miles, 2004; Tripathi, 2005; Belachew et al., 2011). Species of mushroom are considered as a source of protein and possessing high medicinal and economical values (Chang and Miles, 2004; Bhupinder and Ibitwar, 2007). Mushroom farming has two inseparable phases; spawn production and fruiting body cultivation. Spawn is the planting seed of mushroom and technically, it is an expanding mushroom mycelium colonizing a given substrate media (Oei, 2003). Currently, edible mushrooms are cultivated in more than 100 countries (Chang, 2006). The main constraints facing the majority of mushroom producers in developing countries including China is the lack of good quality spawn that meets consumers' preference (Belachew, 2011; Belachewl and Workie,2013). The production of good quality of spawn requires a strict laboratory procedure in which maintaining sanitation and purity of the spawn are critical importance (Wach, 2012). The quality of spawn affects both the yield and quality of cultivated mushroom (Stanley, 2010; Mbogoh et al., 2011). The nutritional supplementation of cultivation substrate is an important cultural practice of mushroom cultivation (Ayodele and Okhuoya, 2007). Most of the growth, yield and quality parameters varied when mushroom was cultivated with different levels of supplements (Mahbuba et al., 2010). Therefore, the substrate supplementation with various additives including nitrogen sources has been reported to improve growth, yield and quality of mushrooms (Jadhav et al., 1998; Khare et al., 2010 and Onyango et al., 2011). They usually change the decomposition rate of substrate components. In most cases the efficiency of agricultural waste acting as substrates is considerably enhanced when supplemented with protein-rich materials (Frimpong–Manso et al., 2011). The various supplements (wheat bran, ammonium sulphate, gram flour, soybean meal, rice bran, mustard cake, cotton seed cake, and molasses) are recommended as substrate supplements prior to spawning to enhance oyster mushrooms (Naraian et al., 2009). The substrate supplementation is a practice used in producing Pleurotus spp. in order to increase its productivity. Inclusion of additives to mushroom substrate is very important especially for substrates having low protein content to enhance the growth and yield of mushrooms (Assan and Mpofu, 2014). Generally, the type of base substrate and additives percentage could affect carbon to nitrogen ratio (C/N), pH, moisture content, compaction, O₂ and CO₂ concentrations and the temperature of the media (Dung et al., 2012 and Randive, 2012).

MATERIALS AND METHODS

The experiment was conducted in Vegetables laboratory, at Horticulture Department, Faculty of Agriculture Al-Azhar University, Cairo and Central Laboratory for Agricultural Climate (CLAC) Minestry of Agriculture, Dokki, during the two successive seasons of 2016/2017 and 2017/2018 under the environmental control of growth chamber. In this study, cultivar of mushroom (Pleurotus ostreatus L starin66) was used to evaluate their characterization under three levels of supplements by using JUNCAO technique. The spore of the cultivar was obtained from CLAC. Four supplements were prepared for this experiment as wheat bran, rice bran, urea, and zinc sulfate. Thirteen treatments of rice straw supplemented with the four nutritional supplements were established. The nutritional supplements were used in three concentrations. The addition of wheat and rice bran were in concentrations of 5, 15 and 25%, while, urea and ZnSO₄ were used in concentrations of 0.5, 1.5 and 2.5%. The nutritional supplements were mixed thoroughly with rice straw. The rice straw material was chopped into small pieces (2-3 cm) using a grinding machine at CLAC. Each treatment was constituted as following formula:

T0 = 100 % Rice straw substrate + 0 % supplement (Control).

T1= 95 % Rice straw + 5% wheat bran t (w/w).

T2= 85 %Rice straw +15% wheat bran (w/w).

T3= 75 % Rice straw + 25% wheat bran (w/w).

T4= 95 % Rice straw + 5% rice bran (w/w).

T5= 85 % Rice straw + 15 % rice bran (w/w).

T6= 75 % Rice straw + 2 5% rice bran (w/w).

T7= 99.5 % Rice straw +0.5% urea (w/w).

T8= 98.5 % Rice straw +1.5% urea (w/w).

T9= 97.5% Rice straw + 2.5% urea (w/w).

T10= 99.5 % Rice straw + 0.5% ZnSO₄ (w/w).

T11=98.5 % Rice straw + 1.5% ZnSO₄ (w/w).

T12= 97.5 % Rice straw + 2.5% ZnSO₄ (w/w).

The moisture content was adjusted to be about 60-70% and pH was adjusted to be 7according toZhanxi and Dongmei, 2008. The rice straw mixing s were filled in polypropylene bags (40 cm length ×18 cm in diameter). 12 bags were packaged for each treatment; each was containing 300g dry substrate. The bags were then marked by permanent marker. All bags were autoclaved at 121°C for two hours and allowed to cool overnight. 

The spawn medium was filled in high-density polyethylene bags each was containing 1 kg. Bags were sterilized at 121°C for 2 hours according toZhanxi and Dongmei, 2008, theninoculated with the spawn on the surface of substrate (about 5 %) under aseptic conditions. Each treatment consists of 12 bags divided into three groups each are four bags representing three replicates. Groups were distributed randomly on shelves in the growth chamber. Bags were allowed to complete mycelial growth in dark at temperature degrees 27°C (the favorable conditions of mycelial growth stage). After colonization (20 days later), the plastic bags were opened from cotton terminal plug, and climatic conditions then were changed; the temperature degree was reduced to be 20°C, the relative humidity was raised to be 90 % and light intensity was adjusted to be 350 lux (the favorable conditions of fruit bodies formation stage). In this experiment, the following measurements were recorded:

Yield characteristics: 1) Number of fruits/bag. 2) Total fruit weight /bag. 3) Biological efficiency/bag.

Characteristics of oyster mushroom

Physical characteristics: 1)Stalk length. 2) Stalk diameter. 3) Cap diameter.

Chemical characteristics of fruit bodies: 1)Potassium (g/100g.d.w.). 2) Nitrogen (g/100g.d.w.). 3) Fat (g/100g.d.w. 4) Protein (g/100g.d.w.).5) Energy (k cal/100g. d. w.).

Determination procedures:

Yield

1) Number of fruit /bag:The harvested mature fruit bodies were counted per bag. 2) Total yield: the first flush, second flush, third flush and fourth flush were weighted in grams and calculated. 3) Biological efficiency: was defined as the ratio of the fresh weight of harvested mushroom over dry weight of substrate (Pokhrel and Ohga, 2007).

Physical characteristics

1) Stalk length (cm): was measured by ruler from branching start point of junction. 2) Stalk diameter (cm) was measured by Vernier caliper. 3) Diameter of cap of fruit body (cm): was measured by Vernier caliper.

Chemical characteristics

Nitrogen content (g/100g. d. w.): The method for determining the nitrogen content was conducted according to Pella (1990). 2) Potassium content (g/100g. d. w.): was determined using an inductively coupled plasma atomic emission Spectrometer (ICP-AES0) according to Pella (1990). 3) Fat percentage in oyster mushroom fruit body was determined by extracting certain weight of powdered sample with petroleum ether using the Soxhlet apparatus as described in the AOAC(1990). 4). Protein content of the samples was estimated by the macro Kjeldhal method employed to find the total nitrogen content. The contents of total nitrogen were multiplied by a factor of 6.25 to find the crude protein of the mushroom sample according to AOAC (1990).5)Energy [Kcal/100g (d.w)]was determined by the equation of Sharma et al., 2013 as follow= [(protein×4) + (Carbohydrate×4) + (fat×9)].

Table 1. Chemical analysis of raw and spent substrates before and after oyster mushroom cultivation.

Statistical analysis

The experiment was statistically analyzed in a randomized complete block design one-way ANOVA with three replicates. The obtained data was subjected to the analysis of on way ANOVA and means were compared by L.S.D. method at 5% level of significance according to Snedecor and Cochran (1982).

RESULTS

Yield characteristics

Number of fruits/ bag

Data presented in Table (2) showed significant differences in fruit number /bag during the two experimental seasons. The highest fruit number/bag was obtained from wheat bran treatment (17.88 and 17.66), while the second level of supplement gave the best result (12.26 and 12.20) in the both seasons respectively. The interaction between treatments and additive levels exhibited highest fruit number/ bag 23.00 and 22.66) which obtained from wheat bran with the second level in the both seasons respectively.

Total weight of fruits /bag

The recorded data in Table (3) revealed significant differences in total weight of fruits/bag in the both seasons. The higher total weight of fruits /bag resulted from wheat bran treatment (248.66 and 244.77 g/bag), in contrast the second level of supplement which gave the heaviest weight (217.64 and 202.68 g/bag) during the two seasons respectively. The interaction between treatments and additive levels showed the highest total weight of fruits/bag (322.33 and 309.00 g/bag) which found in wheat bran with the second level of supplement in the both seasons respectively.

Table 2. Effect of mixing rice straw substrate with different levels of supplements on number of fruits/bag of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 3. Effect of mixing rice straw substrate with different level of supplements on the total weight of fruits/bag (g) of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Biological efficiency/bag

The data tabulated in Table (4) showed significant differences in biological efficiency/bag in the first and second seasons. The highest biological efficiency/bag was obtained from wheat bran treatment (82.88 and 81.81%), while the second level of supplement gave the best result (76.54 and 71.25 %) during the two seasons. The interaction between treatments and additive levels showed the highest biological efficiency/bag (107.44 and 102.99 %) was noted from wheat bran with second level in both seasons respectively.

Characteristics of oyster mushroom

Physical characteristics

Stalk length.

The recorded values in Table (5) cleared significant differences in stalk length during the two seasons. The tallest stalk length resulted from wheat bran treatment (4.45 and 4.49 cm), in contrast the second level of supplement which gave the longest stalks (3.73 and 3.71 cm) in the first and second seasons. Interaction between treatments and additive levels showed the higher stalk length (5.06 and 4.92 cm) was found from urea with the third level of supplement during the two experimental seasons.

Stalk diameter

The recorded numbers in Table (6) showed significant differences in stalk diameter during the two seasons. The largest stalk diameter was noted from wheat bran treatment (2.23 and 2.22 cm), while the third level of supplement gave the best result (1.81 and 1.82 cm) in the first and the second seasons. The interaction between treatments and additive levels showed highest value of stalk diameter (2.50 and 2.45 cm) was found from wheat bran and the second level during the both experimental seasons

Table 4. Effect of mixing rice straw substrate with different levels of supplements on the biological efficiency/bag of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 5. Effect of mixing rice straw substrate with different levels of supplements on the stalk length cm of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 6. Effect of mixing rice straw substrate with different levels of supplements on the stalk diameter of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 7. Effect of mixing rice straw substrate with different levels of supplements on the cap diameter of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Cap diameter

The data in Table (7) showed significant differences in cap diameter during the both experimental seasons. Largest cap diameter resulted from wheat bran treatment (10.55 and 10.63 cm), while the second level of supplement gave the largest one (9.15 and 8.98 cm) during the two seasons. The interaction between treatments and additive levels show best value of cap diameter (13.56 and 13.71 cm) was obtained from wheat bran with the second level of additive during the two seasons, respectively.

Chemical characteristics:

Nitrogen

The data presented in Table (8) showed significant differences in the nitrogen content during the two experimental seasons. The highest value of nitrogen content was noted from wheat bran treatment (0.98 and 0.97 g/100g,), in contrast the second levels of supplement gave the higher result (0.83 and 0.83g/100g) during the two seasons. The interaction between treatments and additive levels showed best value of nitrogen content (1.25 and 1.22g/100g) was found from wheat bran with second level in the two seasons respectively.

Potassium

The recorded value in Table (9) showed significant differences in potassium content of the fruits in the two experimental seasons. The higher value of potassium content (1.16 and 1.03 g/100g) was obtained from rice bran treatment, while the second levels of supplement gave the higher result (0.85 and 0.79g/100g) during the two seasons. The interaction between treatments and additive levels showed best value of potassium content (1.71 and 1.35g/100g), which was found from rice bran with second level in the two season.

Table 8. Effect of mixing rice straw substrate with different levels of supplements on the nitrogen content diameter fruits of Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 9. Effect of mixing rice straw substrate with different levels of supplements on the potassium contentof Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Fat content

The results data in Table (10) showed significant differences in fat content of the fruits in the first and the second seasons. The higher value of fat content (0.51 and 0.50 g/100g) was obtained from rice bran treatment, while the second levels of supplement gave the higher result (0.44 and 0.44g/100g) during the two seasons respectively. The interaction between the treatments and additive levels showed the best value of fat content (0.58 and 0.57g/100g) was found from rice bran with first level during the two seasons.

Protein

The presented data in Table (11) exhibited significant differences in the protein content of the fruits during the two seasons of 2016/2017 and 2017/2018. The highest value of protein content was obtained from wheat bran treatment (4.18 and 4.08g /100g,), while the second levels of supplement gave the highest result (3.57 and 3.51g/100g) in the two seasons. The interaction between the treatments and the additive levels showed best value of protein content (5.32 and 5.21g/100g) was found from wheat bran with the second level during the both seasons respectively.

Energy (kcal/100g. d. w.)

The presented data in Table (12) showed significant differences in the energy content of fruit bodies during the two experimental seasons. The highest value of energy content was found from wheat bran treatment (175.66 kcal/100g) in the first season and with rice bran (153.33 kcal/100g) in the second season. The first level of supplement gave the higher result (149.57 kcal/100g in the first season and 148.04 kcal/100g) during the second season. The interaction between treatments and additive levels showed the best value of energy content (162.81 and 158.12 kcal/100g) was found from wheat bran with second level during both seasons respectively.

Table 10. Effect of mixing rice straw substrate with different levels of supplements on the fat contentof Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 11. Effect of mixing rice straw substrate with different levels of supplements on the nitrogen contentof Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.

Table 12. Effect of mixing rice straw substrate with different levels of supplements on the energy contentof Pleurotus ostreatus during the two seasons of 2016/ 2017 and 2017 /2018.