Wild edibile mushroom Termitomyces spp. for mycoprotein production

Abstract

The present study entitled “Wild edible mushroom Termitomyces spp. for mycoprotein production, was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2020-2022 with an objective to collect and identify the native isolates of Termitomyces spp., in order to determine the optimal conditions for mycelial biomass cultivation and, exploiting the potential of this mushroom for mycoprotein production. A survey was conducted in agro ecological units 8, 9 and 12 of Kerala, during the South West and North East monsoon periods of 2021 and 2022. Twenty six native isolates of Termitomyces were collected from Thiruvananthapuram and Kollam districts. The most distinguishing characters of this mushroom is the presence of an umbonate cap with a prominent perforatorium and a subterranean pseudorhiza. Identification of species were carried out based on macro and micro morphological characters. The macro-morphological characterisation revealed that the cap size varies enormously between the species. The colour of the cap varied from white-cream to grey, light brown to dark brown between species. The pseudorhiza length varied from none (Termitomyces microcarpus) to 35 cm (Termitomyces heimii). The stipe was mostly cylindrical, smooth and glabrous. The spore print was pink in colour. Micro- morphological characterisation revealed that the basidia (18- 30 μm x 5 -9.5 μm) were clavate, bearing four sterigmata, cystidia (24-49 μm x 8-28 μm) were clavate to pyriform, hyaline and the basidiospores (5.5-8.5μm x 3.5-6 μm) were hyaline, ovoid to ellipsoid in nature. Based on morphological characteristics, twenty six Termitomyces samples were identified as ten species. The species confirmed through molecular characterization include Termitomyces eurrhizus, Termitomyces striatus, Termitomyces cylindricus, Termitomyces fuliginosus, Termitomyces microcarpus (large form and small form), Termitomyces radicatus, Termitomyces robusts, Termitomyces sp (1), Termitomyces sp (2) and Termitomyces heimii. Among the nine species, Termitomyces sp (1) and Termitomyces sp (2) were identified as two new species of Termitomyces, the first record from Kerala. It was observed that T. microcarpus (large form and small form) was the most commonly occurring and widely distributed species in Thiruvananthapuram and Kollam districts followed by T. fuliginosus. Cultural studies showed that potato dextrose peptone agar was the best media for mycelial growth of Termitomyces spp. Significantly the largest colony diameter and highest biomass yield of all isolates were observed on potato dextrose peptone agar. Termitomyces eurrhizus (best isolate) showed the largest colony diameter (7.800 cm ±0.100) and biomass yield (1.675 ± 0.006) when compared with other isolates. The growth response of T. eurrhizus to various carbon sources in basal medium (potato dextrose peptone broth) was tested. Higher mycelial biomass production was found in dextrose as carbon source. Peptone was the best nitrogen source to promote higher mycelial production. The optimum temperature, pH and light intensity were identified as 300C, 5.5 and 2000 lux respectively. Mycelial production was nil at 150C, 200C and 350C. The lower and higher pH (4.5 and 7.5) retarded the mycelial growth. The best two isolates (T. eurrhizus, and T. fuliginosus) were used for mycoprotein production. Pelletization was achieved in 100 ml potato dextrose peptone broth of pH 5.5 at 150 rpm in light (2000 lux) after incubation for 20 days at 29±10C. The two isolates produced good pellets evidenced by micro and macro pellets. Spherical to oval compact pellet morphology was common. The most promosing srain was T. eurrhizus which produced brownish to light orange coloured smooth spherical to oval compact pellets (diameter: 1-12 mm). T. fuliginosus produced whitish to light brown coloured pellets (1-11 mm). The proximate analysis of mycoprotein pellet revealed the constituents including crude protein (25. 7%), carbohydrate (36. 59%), fibre (9.91%) fat (3%) and ash (12.3%). The protein content was found to be more in the pellet (25.7%) as compared to the mushroom fruiting body (21.48%). In view of difficulty of domestication of the wild edible mushroom, Termitomyces spp., the only way to exploit the potential is through mycelial biomass production by submerged culture. The present study revealed the possibility of utilizing T. eurrhizus and T. fuliginosus for mycoprotein production.