1993

Itävaara, Merja

Different cultivation methods were compared in order to determine the best method for the large-scale production of shiitake liquid spawn. Liquid spawn has several advantages which include easy and efficient inoculation into the commercial sawdust medium. Production of the liquid spawn is also faster than growing sawdust or grain spawn. Fermenter spawn was the most suitable for large-scale production and adapted well in the supplemented sawdust medium. The method is non-labourous, and vigorous spawn is produced in only 3-5 days. The drawbacks of liquid spawn are a tendency for degeneration and mutation, after repeated subculturing. Genetic changes in the spawn are difficult to detect before fruiting. Therefore, methods for identifing L. edodes strains and species were developed. Esterase and total protein profiles of the vegetative hyphae were used to identify the strains and also to detect any possible changes in them. Either L. edodes strains or different species of wood-rotting fungi were characterized by changing the pH gradient of the gel in isoelectric focusing. A non-toxic stain ABTS was introduced and used to detect laccase activity during the growth of L. edodes mycelium in the liquid and agar medium, wood or sawdust. A spontaneous shiitake mutant strain appeared after repeated subculturing of the normal strain. The normal strain (2105) was one of the best commercially produced strains with good quality of the fruiting bodies and high yield production. The mutant strain (2105D) produced abnormal fruiting bodies in the supplemented sawdust medium, and the total yield of fruiting bodies decreased. Characteristics of the mutant were compared to those of the normal strain. Abnormal fruiting was found to result from changes in carbohydrate and protein metabolism. There were several qualitative and quantitative differences in the intra- and extracellular enzymes of the vegetative mycelium in the mutant and the normal strain. Furthermore, utilization of the carbohydrate compounds in the medium was different from that of the normal strain.