Abstract: The yield of Lentinus squarrosulus (Mont) singer was evaluated following its cultivation on sawdust from seven economic trees (Mansonia altissima, Piptadeniastrum africanum, Nesogordonia papaverifera, Combretodendron macrocarpum, Terminalia sp., Khaya ivorensis and Brachystegia nigerica). The sawdust in each case was supplemented with 20% oil palm fruit fibers. Good growth was observed in all the sawdust except Combretodendron macrocarpum. Between the control and each sample, differences in mean mycelial density were significant (p = 0.05) but differences among the different supplemented sawdust media were not. Supplementation with 20% oil palm fruit fibers advanced the time of primordial emergence and enhanced the fresh weight and number of flushes of the mushroom. The sawdust giving the highest yield was Brachystegia nigerica while the one with the lowest was Combretodendron macrocarpum.
INTRODUCTION
The history of mushroom cultivation is traced to the Romans. In early times, cultivation failed because the biology of fungi was not understood and this led to the initial problems of mushroom cultivation (Oei, 1996; Stamets, 2000). Today, there is a better understanding of the biology, nature and development of many species of edible mushroom (Isikhuemhen et al., 2000; Okhuoya, 2000; Okhuoya et al., 2000; Kurtzman, 2000; Martinez-Carrera, 2000; Wuyep et al., 2002).
In many countries, particularly developed countries, mushroom cultivation and its products yield a lot of income and enhanced dietary meals and improved health of the people (USDA, 2000; Mattila et al., 2001; Mau et al., 2001, 2002; Wasser, 2002; Chu and Chao, 2002; Akpaja et al., 2003). Agricultural wastes, wild grasses and industrial wastes that include sawdust and leaves of many plants, rice bran and wheat bran which are generally abundant in many countries and cause pollution problems are utilised as raw materials in preparing substrates for the growth of mushroom mycelia and fruit bodies (Isikhuemhen et al., 2000; Okhuoya, 2000; Osemwegie et al., 2002; Joshua and Agina, 2002; Kuforiji et al., 2003; Agina and Joshua, 2004; Chiroro, 2004; Okhuoya et al., 2005). In order to enhance mycelial and fruit body growth, these substrate materials commonly are supplemented with nutrients that are rich sources of nitrogen, vitamins and carbohydrate (Royse et al., 1990, 1991; Royse, 1996; Isikhuemhen et al., 1999; Stamets, 2000; Chiroro, 2004). The supplementation enhances yield in several mushrooms as it provides extra nitrogen or easily degradable carbohydrates or both. In turn these extra nutrients improve flavour production, quality and shelf life of cultivated mushrooms (Mau et al., 1991; Chang, 1996; Isikhuemhen et al., 1999; Chiroro, 2004; Okhuoya et al., 2005). In addition, supplementation improves the biological efficiency of mushrooms.
The present study was undertaken in order to evaluate the mycelial growth and yield of Lentinus squarrosulus on different sawdust of economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF). The overall significance of this is that sawdust is a necessary (waste) product from economically important trees that are exploited to yield timber. Although sawdust is used predominantly as domestic fuel nowadays, its economic advantage would be much higher if channelled to mushroom cultivation. That would also reduce environmental pollution which would otherwise result from burning the sawdust.
MATERIALS AND METHODS
Sawdust from Mansonia altissima, Piptadeniastrum africanum, Nesogordonia papaverifera, Combretodendron macrocarpum, Terminalia sp., Khaya ivorensis, Brachystegia nigerica was obtained during timber processing from Uwasota sawmill at Uwasota street in Benin City, Nigeria. Calcium carbonate (CaCO3) was bought from a chemical dealer in Benin City, Nigeria while sugar was bought at Uselu market in Benin City, Nigeria. Oil Palm Fruit Fibers (OPFF) were collected from an oil mill factory in Benin City, Nigeria. Cellophane bags (15x30 cm) were purchased in the market for the study. The study was carried out at the Department of Botany, University of Benin, Benin City, Nigeria in May, 2005.
Each sawdust type was mixed 1% CaCO3, 1% sugar and 20% OPFF on oven dry weight basis. They were composted separately by adding enough water and heaping up to ferment for 7 days with turning every 2 days (Quimio et al., 1990). The moisture content of the fermented sawdust was adjusted to 75% with sterile distilled water.
Five hundred grams oven dry weight equivalent of the fermented and moistened substrates were loaded into cellophane bags measuring 15x30 cm each. Five replicate bags were prepared for each treatment A polyvinyl chloride (PVC) pipe measuring 5 cm wide and 3 cm long was passed through the top of each bag. Thereafter, the mouth of the bag was plugged with cotton wool and covered with foil paper.
The bags were then loaded into a steamer and steamed for 4 h at the temperature of about 70°C. They were allowed to cool down to ambient temperature before they were inoculated at 5% level of spawning. After complete colonization of the substrates, the bags were opened for fruiting. This was followed by periodic watering of bags with sterile distilled water. The environment was ventilated for adequate aeration.
The following parameters were determined:
| • | Time for complete colonization. |
| • | Time of primordial emergence. |
| • | Fresh weight and dry weight of mushroom. |
| • | Flush pattern. |
| • | Percentage organic matter loss (calculated by subtracting the weight of spent substrate from dry weight of substrate divided by dry weight of substrate and multiplied by hundred). |
| • | Percentage biological efficiency (calculated by fresh weight of mushroom divided by the dry weight of substrate and multiplied by hundred). |
The experiment was arranged as a complete randomised design and the results were analysed using simple descriptive statistics such as mean and standard error. Mean was separated using analysis of variance (ANOVA).
RESULTS
Supplementation of sawdust from seven economic trees with 20% oil palm fruit fibers enhanced the mycelial growth and sporophore yield of Lentinus squarosulus. Mean mycelial density was higher in supplemented sawdust than control (sawdust only) (Table 1). There was a significant difference in mean mycelial density (p = 0.05) between control and each sample but none among the different sawdusts.
The time of primordial emergence also varied between the control and the supplemented sawdust. The first appearance was on control of Piptadeniastrum africanum (40.66±0.88 days) and followed by Combretodendron macrocarpum (49.67±5.93 days). The first emergence in supplemented substrates was also in Piptadeniastrum africanum (55.00±1.00 days) followed by Brachystegia nigerica (56.33±1.20 days). The latest emergence of sporophore in the control was in Terminalia sp. (63.60±1.16 days) while the latest emergence on supplemented substrates was observed on Combretodendron macrocarpum (61.33±5.46 days) (Table 2). There was significant difference among the controls (p = 0.05) while there was no significant difference among the treated substrates at p = 0.05.
Mean fresh weight was higher in all the treated sawdust than in the controls except in Combretodendron macrocarpum. The highest yield on treated sawdust was on Brachystegia nigerica (46.10±1.5 g) while the least was Combretodendron macrocarpum (21.63±5.90 g). In the control, the highest yield was on Brachystegia nigerica (32.10±1.56 g) while the least was on Terminalia sp., (5.20±0.31 g) (Table 3).
Percentage biological efficiency was higher in treated sawdust than in the
control. The highest biological efficiency was observed on treated sawdust of
Brachystegia nigerica (8.13%) while the least was on Piptadeniastrum
africanum (3.94%). In the control, Mansonia altissima has the highest
biological efficiency (4.27%) while the least was observed on Terminalia
sp. (0.87) (Table 4). The mean number of flushes was almost
the same except in the control of Nesogordonia papaverifera, Khaya
ivorensis and Brachystegia nigerica which had higher mean numbers
of flushes than the treated sawdust (Table 5).
| Table 1: | Mean fresh weight (g) of mycelia of Lentinus squarosulus on sawdust of selected economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
| Table 2: | Time of sporophore emergence of Lentinus squarosulus on sawdust of selected economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
| Table 3: | Mean fresh weight of Lentinus squarosulus on selected economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
| Table 4: | Percentage biological efficiency of Lentinus squarosulus on selected economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
| Table 5: | Mean number of flushes of Lentinus squarosulus on sawdust of selected economic trees supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
| Table 6: | Percentage organic matter loss in substrates of Lentinus squarosulus on sawdust supplemented with 20% Oil Palm Fruit Fibers (OPFF) |
| SD = Sawdust | |
The total percentage organic matter loss was higher in control than in the treated substrates except in Piptadeniastum africanum and Combretodendron macrocarpum which have the highest percentage organic matter loss (Table 6).
DISCUSSION
Supplementation of substrates has become one of the major aspects of mushroom cultivation. This is in order to boost the yield of mushrooms. Lentinus squarrosulus grew better on the different sawdust when 20% oil palm fruit fibers were added. The supplement obviously modified the substrates, hence, there was a better conversion and utilisation of the substrates for mycelial growth and sporophore yield. This is in line with the report of Zadrazil (1993) who reported that supplements usually change the decomposition rate and the sequence of decomposition of substrate components during mushroom growth. Supplementation of substrates with different levels of carbon and nitrogen-based additives has been shown to enhance mushroom production (Royse et al., 1990, 1991; Zadrazil, 1993; Fasidi and Kadiri, 1993; Royse, 1996; Isikhuemhen et al., 1999; Stamets, 2000). Royse et al. (1990) have reported formulas incorporating supplements, particularly grains in mushroom substrates. In this study, all the sawdust types, supplemented with 20% OPFF showed variable results in supporting mycelial density and sporophore yield of Lentinus squarrosulus.
There was a higher mycelial density in all the sawdust types when supplemented with 20% OPFF except in Terminalia sp. It does appear that OPFF at 20% failed to promote mycelial formation in Terminalia sawdust. This may be due to the carbon to nitrogen imbalance in the Terminalia sawdust (Stamets, 2000; Okhuoya et al., 2005). It could also be due to the fact that the concentration used fell below or above the required concentration that can promote mycelial growth (Stamets, 2000; Okhuoya, 2005).
The supplement reduces the time of sporophore emergence in Mansonia altissima, Nesogordonia papaverifera and Terminalia sp. and there was a delay in sporophore emergence in Piptadeniastrum africanum, Combretodendron macrocarpum, Khaya ivorensis and Brachystegia nigerica. This observation is contrary to the report of Fasidi and Kadiri (1993), Royse (1996), Isikhuemhen et al. (1999) and Kuforiji et al. (2003) who reported that supplementation stimulates both mycelial extension and sporophore emergence and yield in Lentinus subnudus and Pleurotus tuberregium on agricultural wastes.
There was higher fresh weight of Lentinus squarrosulus on all sawdust supplemented with 20% OPFF except on Combretodendron macrocarpium. This is in line with the report of Royse and Schisler (1986), Han et al. (1981) who reported higher yield of Shiitake mushrooms when supplements were added to their substrates at different concentrations. The stimulatory effect observed with 20% OPFF may be due to the nutrients in OPFF which stimulate the utilization of the sawdust effectively. The lower fresh weight observed in Combretodendron macrocarpium may be due to the inability of the 20% OPFF to stimulate the growth of Lentinus squarrosulus on the sawdust (Stamets, 2000). According to Han et al. (1981), there is an optimum concentration of different supplements and on different substrates which can enhance or stimulate mycelial growth and sporophore yield of mushrooms. This may be the case in Combretodendron macrocarpium. The 20% OPFF may be below or above the concentration needed to stimulate sporophore yield in Lentinus squarrosulus.
A higher Biological Efficiency (BE) was observed in supplemented substrates with 20% OPFF. This supported the works of Fasidi and Kadiri (1993), Royse (1996) on Pleurotus tuberregium and Lentinus subnudu, respectively. The observed variation in organic matter loss was in line with the report of Fasidi and Kadiri (1993), Isikhuemhen et al. (1999) who observed that the stimulatory concentration of supplements varies according to the substrates and ability of the supplement to modify the substrate for the mushroom to utilize effectively.
This study showed that OPFF at 20% concentration significantly enhanced the yield of Lentinus squarrosulus on different sawdusts tested. It therefore means that OPFF can be employed as supplement in the cultivation of Lentinus squarrosulus. This could lower the cost of production. However, the limiting concentration of OPFF for yield enhancement needs further investigation.