Effect of temperature and hydraulic retention time on volatile fatty acid production based on bacterial community structure in anaerobic acidogenesis using swine wastewater
Woong Kim, Seung Gu Shin, Juntaek Lim, Seokhwan Hwang
Abstract To investigate the effect of hydraulic retention time (HRT) and temperature (T) on bacterial community structure and volatile fatty acids (VFAs) production of an acidogenic process, and VFA production and changes in the bacterial community in three identical automated anaerobic continuously-stirred tank reactors were analyzed using response surface analysis (RSA) and nonmetric multidimensional scaling (NMDS). For RSA, 11 trials were conducted to find the combination of T and HRT under which VFA production was greatest; VFA production was affected more by HRT than by T. To identify the bacterial community structure in each trial, DNA from each experimental point of the RSA was analyzed using denaturating gradient gel electrophoresis (DGGE), and eight bacteria species were detected. NMDS was conducted on band intensities obtained using DGGE, and bacterial community structure was affected more by T than by HRT. Taken together, these results suggest that VFA production during acidogenesis was more dependent on the physicochemical properties of acidogens, such as their specific growth rate or contact time with of substrates, than on changes in the microbial community.
Fig. 1 Bacterial DGGE profiles of the PCR products amplified with 16S rRNA gene primers at each trial of response surface analysis (SL initial seed, SW swine wastewater as a substrate of acidogens), lane labels show each trial for response surface analysis (T1, T4, and T7, T = 40 C; T2, T5, and T8, T = 50 C; T3 and T6, T = 60 C; T1–3, HRT = 2.5 d; T4–6, HRT = 1.5 d; T7–8, HRT 0.5 d; Trial at T = 60 C and HRT = 0.5 d was not detected; Codes on the DGGE gel identify the bands excised for sequencing)
Fig. 2 ANOVA results of quadratic model for optimization of
acidogenesis using swine waste with respect to two independent
variables and their interactions
Fig. 3 NMDS map of bacterial communities analyzed from DGGE profiles (filled circles, designated as T1–8, indicate trials of response surface analysis; open circle, designated as abbreviated letters, represent microbial species)