Induction Of Endoglucanse Expression By Different Carbon Sources In Volvariella Volvacea

The edible straw mushroom, Volvariella volvacea, produces a family of cellulases that hydrolyse the cellulose component for fungal growth. However, the cellulose polymer is too large to enter the fungal hypha, therefore, the cellulolytic enzymes have to be secreted to the external environment. The previous studies showed that V. volvacea can produces produces three kinds of cellulose, namely, endoglucanse(EC3.2.1.4), cellobiohydrolase(EC3.2.1.91),β-glucosidase(EC3.2.1.21), and so on. This article elaborately studied the induction mechanism of different carbon sources to cellulase synthesis of V. volvacea, evaluated the endoglucanse producing property.Fungal cellulases is a sort of induction enzyme, and the carbon source is the major part of induction. Western blotting was chosen to detect the expression of EG1 which was grown on liquid medium containing different carbon sources in this experiment. It was shown that the expression of EG1 can be induced byα-lactose, cellobiose, carboxymethyl cellulose, avicel, wheat bran;EG1 was strongly expressed when V. volvacea was grown in liquid medium containing microcrystallite cellulose as carbon source during 10 days culture;The expression level of EG1 was associated with mycelia colonization and fruit body development when V. volvacea was grown on rice strawcompost. The expression of EG1 was then increased in accordance with the development of fruit body, and reached at maximal level at mature stage.In order to futher study the expression of EG1,α-lactose,cellobiose and sorbose were used to induce the expression of EG1. It was foundα-lactose and cellobiose can induce the high expression of EG1, but sorbose can not; when different concentrations ofα-lactose and cellobiose were added, a unconspicuous effect on cellulose formation was found after 24 hours. Expression of EG1 reached about the maximum level when 0.5% used forα-lactose and 2% used for cellobiose. When lactose and sorbose were added, expression of EG1 was restrained, but when cellobiose and sorbose were added, the induction was as usual. Whenα-lactose and cellobiose were added together, the expression of EG1 was delayed.In the experiment, RT-PCR was used to study the eg1expression at the transcriptional level in V.volvacea. Eg1 expression was observed 3 hours after the addition ofα-lactose, then it is strongest in 4.5 hours. In the following 9 hours, the expression became weaker, then it is extraordinary weak after 24 hours.