Xylanase enzyme is an extracellular enzyme that has the ability to hydrolyze xylan to xylose. Xylanase can be produced by thermophilic bacteria and is a natural xylanase that is active and stable at high temperatures and alkaline pH, so it has the potential to be used in industrial and biotechnology fields. One industry that utilizes xylanase enzymes is the pulp and paper industry. At present, the pulp bleaching process carried out in Indonesia consists of a bleaching process using chlorine or hydrogen peroxide. The substitution of the use of chlorine with xylanase enzymes is a worthy alternative to reduce the impact caused by the use of chlorine in the pulp bleaching process. This study aims to determine the potential of thermophilic bacterial xylanase enzymes on the brightness of the pulp, and determine the brightness of the pulp at variations in temperature and pH on pulp fermentation. The pulp is fermented with temperature variations (50ºC, 55ºC, 60ºC, 65ºC, 70ºC, 75ºC, 80ºC) and pH (7; 7.5; 8; 8.5; 9; 9.5; 10). The optimum temperature and pH that produces the lowest kappa number and highest enzyme activity is at 60ºC and pH 8.5.