Bulletin Spring‧Summer 1995

They Mushroom on Different Materials A study of enzyme p r o d u c t i o n by mushrooms to t u rn waste m a t e r i a l s i n to food and value-added compounds Mushrooms — A Multi-usage Wonder The technical advances made during recent decades have, along wi th myriad other implications, resulted in edible mushroom cultivation attaining global dimensions. Since cultivated mushrooms can be grown under different climatic conditions on cheap, readily available waste materials, they represent a solution to many of the world's current problems, including protein shortages, resource recovery and re-use, and environmental management. The cultivation of edible mushrooms is a prime example of how low-value waste — which is produced primarily through the activities of the agricultural, forest and food-processing industries —can be converted to a higher value commodity useful to mankind. Many varieties of mushrooms are valued greatly as nutritious food sources, as tonic foods, and as important sources of medicinal compounds —an t i - t umou r / an t i - v i r al agents and other pharmaceutically-active components. A number of proprietary products, including cosmetics, beverages and health foods, are marketed currently and the demand for such products is expected to increase. Nutrition for Mushrooms 一 Different for Different Species Mushrooms are not chlorophyllous plants, i.e. they do not have the green pigment called chlorophyll that enables plants to utilize energy from sunlight to change chemicals into substances necessary for growth, a process commonly known as photosynthesis. Instead, mushrooms produce a wide range of extracellular enzymes, and it is these extracellular enzymes that enable them to degrade complex organic matter into soluble substances which can then be absorbed by the mushroom for purposes of nutrition. The growth and fruiting of an individual mushroom species on a particular waste material will hence depend largely upon the ability of that mushroom to produce the enzymes essential to degrade the major components of the waste particular (or its growth 'substrate'), and thereafter absorb it as food. Three Enzymes and Five Species of Mushrooms under Scrutiny The materials that are most widely adopted for mushroom cultivation are 'lignocellulosic' materials — the major components of which are cellulose, hemicellulose and lignin. Together these three polymeric substances form the bulk of most plant cell walls. Dr. John Buswell and Prof. S.T. Chang of the Department of Biology have undertaken a study entitled 'An investigation of extracellular enzyme production by selected edible mushroom species, and their ability to utilize different lignocellulosic wastes as growth substrate'. The main aim of this research is to investigate the production of three enzymes — cellulases, hemicellulases and ligninases — by five commercially important edible types of mushrooms, to decompose the cellulose, the hemicellulose, and the lignin respectively. This project won a competitive grant of HK$682,000 from the Research Grants Council in 1992. The experimental results so far have revealed a wide range of ability among different edible mushrooms to produce the enzymes necessary to degrade individual components of lignocellulose. Research 16