Background: The Tibetan pig is a pig breedwith excellent grazing characteristics indigenous to the Qinghai–Tibet
plateau in China. Under conditions of barn feeding, 90% of its diet consists of forage grass, which helps meet its
nutritional needs. The present study aimed to isolate and identify a cellulolytic bacterium from the Tibetan
pig's intestine and investigate cellulase production by this bacterium. The study purpose is to provide a basic
theory for the research and development of herbivore characteristics and to identify a source of probiotics
from the Tibetan pig.
Results: A cellulolytic bacterium was isolated from a Tibetan pig's intestine and identified based on
morphological, physiological, and biochemical characteristics as well as 16S rRNA analysis; it was designated
Bacillus subtilis
BY-2. Examination of its growth characteristics showed that its growth curve entered the
logarithmic phase after 8–12 h and the stable growth phase being between 20 and 40 h. The best carbon
source for fermentation was 1% corn flour, while 2% peptone and yeast powder compound were the best
nitrogen sources. The initial pH during fermentation was 5.5, with 4% inoculum, resulting in a high and stable
amount of enzyme in 24–48 h.
Conclusions: The isolated BY-2 strain rapidly grew and produced cellulase.We believe that BY-2 cellulase can help
overcome the shortage of endogenous animal cellulase, improve the utilization rate of roughage, and provide
strain sources for research on porcine probiotics.
