Abstract

Sediments of North Delta (Egypt) are a rich source of many thermo-tolerant bacteria, which could be used as a good source of many enzymes. Sediment samples were collected from six different sites in North Delta region. The counts of thermo-tolerant marine bacteria (at 55°C) in sediment samples ranged from 9.8x10² to 6.8x10³ CFU g^-1. It was found that the occurrence of thermo-tolerant bacteria in North Delta sediments at 55°C reached 11.1% with respect to the total viable count at 30°C. Five of seven selected thermo-tolerant bacterial isolates showed optimum growth at pH 9 and NaCl concentration of 4% (w/v) after 24 h of incubation at 55°C. Two thermo-tolerant marine bacteria were selected and identified as Achromobacter sp. HEGN 014 and Virgibacillus pantothenticus HEGN 114 using 16S rDNA analysis. Their sequence similarities were 96 and 97%, respectively. Their optimum growth was at pH 9 and NaCl concentration of 4% (w/v) with tolerance to higher concentration of 7 and 9% (w/v), respectively. Moreover, both strains were investigated to produce an extracellular lipase, while they showed no productivity for cellulase, chitinase or protease at 55°C, however, gelatinase was produced only by V. pantothenticus HEGN 114. Antibiotics resistance was observed for Achromobacter sp. HEGN 014 and V. pantothenticus HEGN 114. The optimum reaction temperatures for the purified lipases from both strains were the same at 35 and 55°C. The amino acid analysis showed that arginine represented 89.982 mmole of total detected amino acids of lipase produced from Achromobacter sp. HEGN 014 with tolerance to higher concentration of 7 and 9% (w/v) NaCl.

Key words: Achromobacter sp., Virgibacillus pantothenticus, thermo-tolerant, lipase.