Enzymatic Characterization Of Kitchen Waste During Anaerobic Digestion Process

Inoculated with granular sludge, cumulative gas and methane production from kitchen waste were studied with the addition of either promoting factor (yeast powder) or inhibitor (chloramphenicol). Some physical and chemical parameters (organic acids,pH,SCOD), and coenzyme F420,dehydrogenase and some hydrolase (β-glucosidase,BAA-hydrolysing protease and alkaline phoshpatase) were also studied under this condition, proteomics profiling was also investigated at the maximum enzyme activities in the anaerobic system. The main research contents and results are as follows:(1) The best TS ratio of kitchen waste and granular sludge was 4:1 (total TS was 15 g). Cumulative gas and methane reached 3130 mL and 2035 mL. under this situation, respectively. Moreover, the percentage of methane was 65% by then.(2) With the addition of yeast powder, cumulative gas and methane were 6410 mL and 2357 mL, respectively, and which were increased by 105% and 118% respectively compared with the control, respectively. However, gas and methane production was 1030mL and 196 mL under the condition of inhibition, which decreased by 67% and 82% in comparison with the control.(3) Compared with control, order of the increase rate of VFA productivity were acetic acid of 94%, propionic acid of 81%, lactic acid of 64%, butanoic acid of 0.6%, while the decrease rate was lactic acid of 74%, propionic acid of 71%, acetic acid of 17%, butanoic acid of 13%. Moreover, SCOD has the same trend as the VFA.(4) With the addition of yeast powder, compared with the control, the activity of coenzyme F420 increased by 39%, dehydrogenase increased by 86%, the activities ofβ-glucosidase,BAA-hydrolysing protease and alkaline phoshpatase increased by 46% and 62% respectively. In contrast, compared with the control, with the addition of chloramphenicol, the activities of these four enzymes decreased by 19%,31%,22% and 35%, respectively. On the other hand, little change was found in alkaline phosphatase activity, it seems that this enzyme was less affected against either the promoting or inhibitory condition. (5) Proteomics profiling was also investigated at the maximum enzyme activities in the anaerobic system. Of the five matched results detected by mass spectrometry. four of them were methyl coenzyme-M reductase, while the other one is alcohol dehydrogenase. Methyl coenzyme-M reductase involved in methane metabolism or folate biosynthesis; while alcohol dehydrogenase was involved in a special Methylmalonyl-CoA pathway.