ScienceAsia 23 (1997): 307-322 |doi: 10.2306/scienceasia1513-1874.1997.23.307

PURIFICATION AND CHARACTERIZATION OF XYLANASES FROM CRYPTOCOCCUS SP. X-1

THUNYA SRIPO^a, TAKESHI OHARA^b AND AMORNRAT PHONGDARA^a

ABSTRACT: The sperm cell fertilization tests using sea urchin, Diadema setosum were conducted to determine the toxicity of cadmium, zinc and copper. Five concentrations for cadmium ranging from 0.32 - 32 mg Cd/L, for zinc ranging from 0.032 - 3.2 mg Zn/L, and for copper ranging from 0.001 - 0.1 mg Cull, plus a control were used to investigate the effects of these metals on sperm viability as indicated by a reduction in fertilization success. This test used a short exposure period, 10 minutes sperm exposure, followed by 10 minutes egg fertilization. The experiments were repeated three times for each metal. The results indicated that copper was the most toxic to D. setosum, followed by zinc and cadmium, respective/y, with toxicity values (EC₅₀s) of 0.017 0.013 mg Cull, 0.38 0.19 mg Zn/L, and 6.28 1.32 mg Cd/L, respectively. These values were calculated based on actual concentrations for cadmium and zinc, and on nominal concentrations for copper.

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Institute of Marine Science, Burapha University, Chon Buri, 20131 Thailand.

Received 15 July 1997