The Potential of Digested Sludge-Assimilating Microflora for Biogas Production from Food Processing Wastes

Abstract

Food processing wastes (FPWs) are residues generated in food manufacturing, and their composition varies depending on the type of food product being manufactured. Therefore, selecting and acclimatizing seed microflora during the initiation of biogas production is crucial for optimal outcomes. The present study examined the biogas production capabilities of digested sludge-assimilating and biogas-yielding soil (DABYS) and enteric (DABYE) microflorae when used as seed cultures for biogas production from FPWs. After subculturing and feeding these microbial seeds with various FPWs, we assessed their biogas-producing abilities. The subcultures produced biogas from many FPWs, except orange peel, suggesting that the heterogeneity of the bacterial members in the seed microflora facilitates quick adaptation to FPWs. Microflorae fed with animal-derived FPWs contained several methanogenic archaeal families and produced methane. In contrast, microflorae fed with vegetable-, fruit-, and crop-derived FPWs generated hydrogen, and methanogenic archaeal populations were diminished by repeated subculturing. The subcultured microflorae appear to hydrolyze carbohydrates and protein in FPWs using cellulase, pectinase, or protease. Despite needing enhancements in biogas yield for future industrial scale-up, the DABYS and DABYE microflorae demonstrate robust adaptability to various FPWs.

Keywords: anaerobic digestion; cellulase; food waste recycling; hydrogen; methane; pectinase; protease.

Figure 1

Denaturing gradient gel electrophoresis (DGGE) band patterns of eubacterial members from subcultured microflorae originating from DABYS-A (a), DABYS-B (b), DABYE-G (c), DABYE-S (d), and DABYE-R (e) seed microflorae. The data display patterns for the 10th subculture fed with FPWs, except for the third subculture fed with orange peel, along with their originating seed cultures. Green, blue, purple, red, orange, and pink arrowheads indicate major characteristic amplicons for the V6–V8 region of the 16S rRNA genes of the Clostridiaceae, Enterobacteriaceae, Pseudomonadaceae, Bacillaceae, Lachnospiraceae, and Oscillospiraceae families, respectively.

Figure 2

Denaturing gradient gel electrophoresis (DGGE) band patterns of methanogen members from subcultured microflorae originating from DABYS-A (a), DABYS-B (b), DABYE-G (c), DABYE-S (d), and DABYE-R (e) seed microflorae. The data display patterns for the 10th subculture fed with FPWs, except for the third subculture fed with orange peel, along with their originating seed cultures. Green, blue, and white arrowheads indicate characteristic amplicons for the V3 region of the 16S rRNA genes of Methanobacteriaceae, Methanosarcinaceae, and unidentified archaeal families, respectively.

Figure 3

Cellulase, pectinase, and protease activities of the subcultures originating from DABYS-A (a), DABYS-B (b), DABYE-G (c), DABYE-S (d), and DABYE-R (e) seed microflorae. The data are presented as the mean ± standard deviation of independent triplicates. The blue-, green-, and orange-colored letters on the columns indicate significant differences at p < 0.05 (Student’s t-test) in cellulase, pectinase, and protease activity, respectively.