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Biological treatment of oil palm empty fruit bunch fibre for Volvariella volvacea (Bul.) Singer cultivation and spent utilization
Dissertation Abstract:
The Malaysian palm oil industry produces about 20 million tons of empty fruit bunches (EFB) annually. The use of EFB for the cultivation of mushrooms such as Volvariella volvacea or straw mushroom offered an alternative solution for sustainable management. However, the low yield of this mushroom remains a barrier to large-scale cultivation, and the spent compost management is not yet well established. Therefore, this research focused on the use of EFB as a substrate for high yield cultivation of Volvariella volvacea and the utilization of the spent compost. To this end, the study is divided into four parts. In the first part, the effects of pre-treatment with effective microorganisms (EM) and composting time of EFB fibers on mycelial growth and yield of Volvariella volvacea were determined. It was determined that EM pre-treatments of 20% and 30% resulted in significantly faster mycelial growth compared to the other treatments. However, it was not significant to the yield. The highest yield of V. volvacea was observed at T2E4 (10d, 30% EM) with 271.5± 57.28 g or biological efficiency (B.E.) of 9.11%. The highest average weight per fruiting body (FB) was obtained at T1E3 (5d, 20% EM) with 14 g, while T2E4 (10d, 30% EM) yielded the highest number of harvested FB with 42. Cellulose, hemicellulose and lignin were reduced in all treatments tested. Both EM dosages and composting times significantly affected the yield of V. volvacea. EFB fibre was a potential substrate for the cultivation of Volvariella volvacea, but the yield was still low compared to the commercial substrate. In the second part, we attempted to improve the yield of Volvariella volvacea using different strategies. Another type of EFB fiber, pellet, was introduced as a growing medium. The best conditions from the previous experiment were applied. It was found that the EFB pellet without composting gave the highest yield of 20.37% biological efficiency (B.E). An additional 8% of rice bran and 7% of fertilizer produced the best yield of 24.83% B.E. with a suitable C:N ratio for fungal growth. Oligochitosan at 0.03% concentration produced the highest % B.E. (29.86) followed by acetate 0.05% (27.45) and foliar 0.03% (23.63). It was found that a higher cellulolytic enzyme was released during pinning compared to post-fruiting except for FPase, which recorded a higher concentration post-harvest. Proximate analysis of fruiting bodies showed no significant difference in the protein content of the samples of different treatments. While fiber, ash, and carbohydrate content of fruiting bodies was in the acceptable range. Booster application during cultivation improved mushroom yield and preserved the proximate quality. The third part of the study deals with recycling spent mushroom compost (SMC) for the extended cultivation of Volvariella volvacea. SMC was tested as substrate in five different ratios of Pellet:SMC (1:0, 1:3, 1:1, 3:1, 0:1). The 2 kg compost was enriched with rice bran, organic fertilizer, and CaCO3 at 8%, 7%, and 5%, respectively. The best substrate for cultivation was Pellet, followed by Pellet:SMC (3:1), which gave B.E. of 16.35 and 15.47%, respectively. Proximate analysis of the fruiting bodies (FB) showed that SMC samples had a lower protein content of 20.01% compared to other samples. FB of P samples produced the highest protein content of 27.28%. No significant difference was observed for fat content in the samples. However, the highest concentration of ash and fiber was determined in sample P:SMC (3:1). Significant reduction of cellulose and hemicellulose was determined in all samples during cultivation, but minimum lignin degradation was observed. The use of SMC as a co-substrate for mushroom cultivation was successfully demonstrated and of high potential. In the last part, the potential of EFB fiber and EFB fiber-based SMC from Volvariella volvacea cultivation as an energy feedstock is tested. The biochemical methane potential (BMP), calorific value (CV), and other analysis such as proximate, compositional and ultimate analysis, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) are also performed. The biomass samples consist of two types of EFB, namely fibers (F) and pellets (P) and SMC from the subsequent cultivation, with samples FS and PS from the first cultivation and FS2 and PS2 from the second cultivation. P has the highest B.E. of 28% compared to 9.83% for F. Subsequent cultivation with FS and PS produces only 2.9 and 6.83% of B.E. A higher amount of methane is measured in P and PS2 samples, while better biodegradability is observed in PS2 and FS2, indicating that subsequent cultivation is a good pre-treatment of the substrate for the anaerobic digestion (AD). CV is highest in F (20.57 MJ/kg), followed by P (19.06 MJ/kg), which is comparable to commercial wood pellets. TGA analysis revealed that EFB pellet-based SMC has higher weight loss on combustion than EFB fiber, affecting its thermal properties. This study proves that the EFB pellet is a suitable substrate for Volvariella volvacea cultivation and its spent compost poses a good potential for energy production and as a co-substrate for extended cultivation.