Influence of temperature on short-chain fatty acid production by pig cecal bacteria in vitro

We studied the effect of incubation temperature on the production of shortchain fatty acids (SCFA) by pig cecal bacteria in vitro in order to assess short-term influences of body temperature on bacterial metabolism in the large intestine. We employed a 200 mL scale continuous culture system using cecal bacteria from commercially slaughtered pigs as innoculum. The culture was maintained at 30, 37, 40 or 42 degrees C and continuously diluted by continuous feeding of bicarbonate buffer (pH 7.4) added with lactose (10 g/L) and by simultaneous continuous efflux both at 4.17 mL/h. We monitored SCFA concentration of the culture for 12 h, which represents their production rate. Concentrations of SCFA increased during the first several hours and plateaued at around 11 h of incubation. Incubation temperature significantly affected mean concentrations from 1 to 12 h of acetic (40 degrees C>42 degrees C= 37 degrees C>30 degrees C), propionic (40 degrees C>42 degrees C=30 degrees C), n-butyric (42 degrees C>37 degrees C>30 degrees C, 40 degrees C>30 degrees C) and n-valeric (42 degrees C=40 degrees C>37 degrees C>30 degrees C) acids, and total SCFA (40 degrees C>42 degrees C= 37 degrees C> 30 degrees C) (p<0.05). These results indicate that both hyperthermia and hypothermia depress the microbial breakdown of carbohydrates.