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 short-chain 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, 3 7, 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.