STUDY ON SUBSTRATE CONTAMINATION OF OYSTER MUSHROOM IN BANGLADESH AND THEIR MANAGEMENT THROUGH AGROCHEMICAL ENRICHMENT AND PASTEURIZATION

Abstract

Survey and laboratory experiments were carried out during the period of 2013 -2016 to study the prevalence of contamination, effect of micronutrient enrichment and different sterilization techniques of substrates of oyster mushroom in Bangladesh. Survey study on 110 mushroom growers of 59 upazillas in 21 districts revealed that oyster mushroom Po was the most cultivated popular species. Seed crisis and spawn contamination were identified as the main problem of farmers where 30% contamination occurred during incubation, 30% in summer and less than 20% in winter. 52.7% farmers conducted substrate sterilization through hot water for 1 hour. Rice straw (55.7%) and saw dust (21.6%) was mainly used as substrate. Trchoderma, Rhizopus, Aspergillus, Penicillium, Alternaria, Ceratocytis, Coprinus, Chaetomium sp. were found to be associated as contaminants where green mold was detected as the major one. Enrichment of substrate with Agrovit plus (1000-5000 ppm), Boron (10000ppm) , 10 ppm Mncl 2 showed better result over control where 3000 ppm Agrovit injection in substrate resulted highest yield (316.6g), increased mushroom harvesting time, less contamination. In addition, the rate of carbohydrate, fiber, protein, moisture and mineral were also increased. Use of chemicals viz, Bavistin (75 ppm), Formalin (500 ppm), Surf-xcel (100 ppm), Hydrogen Peroxide (30000 ppm), Chlorox (1000 ppm), Lime (286 ppm), Manganese chloride (100 ppm) found effective in minimizing the contamination of competitor moulds. The highest growth rate (1.3 cm), biological yield (219.6g/packet), biological efficiency (43.3%) was observed while treated substrate packets with Hydrogen per oxide. Pasteurization techniques of the substrates were standardized for oyster mushroom and it was observed that pasteurization of small bags (500g) for 3 hours were found most ideal for less contamination. Efficiency of steam pasteurization and autoclaving were compared at different time duration to control substrate contamination and the result showed that highest growth rate (1.03cm), better yield performance (311.3g) and the highest biological efficiency (66.01%) with minimum contamination were observed while packets steam pasteurized for three hours. Again, performance parameters such as, economic yield (235.2g) and BE (48.2%) was found while packet treated with 80 0 C for 2 hours. As such pasteurization of rice straw through steam in steel drum for 3 hours in lieu of other treatments namely hot water treatment, chemical treatment or autoclaved treatment would be a viable and promising technique for substrate pre-treatment that can be adopted to produce a good yield of oyster mushroom in most rural areas, where autoclave sterilization may not be feasible. 2