Influence of pH and Temperature on Enumeration of Cellulose- and Hemicellulose-Degrading Thermophilic Anaerobes in Neutral and Alkaline Icelandic Hot Springs.

Cellulose- and hemicellulose-degrading thermophilic anaerobes were enumerated in biomat samples of various temperatures from two different hot springs in the Hverageroi area of Iceland: one spring had a pH near 7, the second had a pH near 9. The most-probable-number technique was used for enumeration of bacteria in the samples, with media at many different temperatures (37 to 90 degrees C) and two pH values (7 and 9). There were generally more xylan-degrading then cellulose-utilizing organisms in both environments. There was no growth at 80 degrees C in the neutral spring or at 37 degrees C in the alkaline spring. However, there were large numbers of both types of organisms in the alkaline spring at 80 degrees C and in the neutral spring at 37 degrees C. No cultures grew from the most-probable-number tubes inoculated with the Hverageroi samples and incubated at 90 degrees C or with media at pH 9. However, xylan-degrading cultures at 70 degrees C were enriched at pH 9 with samples from some other Icelandic hot springs.