Studies on genetic diversity and lentinan production among Lentinula edodes strains

Abstract

Seven strains of Lentinula edodes (LeC, LeI, LeS, OE-38, OE-142, OE-329 and OE-388) were molecularly characterized using RAPD, ITS sequencing, SDS-PAGE and isozyme analysis. Out of twenty primers were used for RAPD fifteen primers gave distinct amplification products. Maximum similarity coefficient (0.716) was obtained between LeC and LeI while minimum similarly coefficient (0.503) was found between LeI and OE 142. ITS sequences indicated that LeC strain was highly divergent from all the other strains in ITS-1, 5.8S & ITS-2 region while LeI strain showed high degree of divergence in ITS‑1 region only. Protein profiling using SDS-PAGE indicated maximum similarity in three strains OE-38, OE-142 and OE-388 with the three bands formed at Rm of 0.02, 0.36 and 0.78 with molecular weight of > 97kDa, 44kDa and 18.7kDa, respectively. Isozyme analysis of L. edodes strains gave two bands for alcohol dehydrogenase, two for malate dehydrogenase and three for peroxidases. Response surface methodology (RSM) was employed to identify the interactions between the operational variables (pH, temperature, incubation period and agitation). The conditions for biomass and polysaccharide production were optimized using Design Expert 8.0 (Stat Ease, Minneapolis, MN). Regression equations were developed with R² value ranging between 0.7204 to 0.9669 indicating high degree of fitness. The cultivation trials of five strains on wheat straw and saw dust with supplementation of wheat bran showed that wheat straw substrate produced maximum biological efficiency at 10 per cent level of wheat bran supplementation in OE-388 (66.8%) and OE-329 (46.2%). In case of sawdust substrate, maximum biological efficiency was obtained at 5 % level of wheat bran supplementation in LeS, OE-142, OE- 388 strains. LeC and LeI strain produced maximum biomass while no fruiting bodies were observed in these strains. Cultivation trials indicated that Le-S, OE-38, OE-142, OE‑329 and OE-388 were the fruiting cultures. The polysaccharides and extracts prepared from all the strains indicate the potential biomolecules present in these strains which could be further purified for the development of nutriceuticals and commercial exploitation. The qualitative and quantitative estimation of lentinan through FTIR spectroscopy showed a prominent band at around 1650 cm^-1 in all the strains. The approximate estimation of lentinan revealed that samples under study contained 0.9mg/mL in the fruiting bodies of OE-388 to 5.4mg/mL in the biomass of OE-142 strain.