Production of H2 from cellulose by rumen microorganisms: effects of inocula pre-treatment and enzymatic hydrolysis

Abstract

H2 production from cellulose, using rumen fluid as the inoculum, has been investigated in batch experiments. Methanogenic archaea were inhibited by acid pre-treatment, which also inhibited cellulolytic microorganisms, and in consequence, the conversion of cellulose to H2. Positive results were observed only with the addition of cellulase. H2 yields were 18.5 and 9.6 mmol H2 g cellulose(-1) for reactors with 2 and 4 g cellulose l(-1) and cellulase, respectively. H2 was primarily generated by the butyric acid pathway and this was followed by formation of acetic acid, ethanol and n-butanol. In reactors using 4 g cellulose l(-1) and cellulase, the accumulation of alcohols negatively affected the H2 yield, which changed the fermentation pathways to solventogenesis. PCR-DGGE analysis showed changes in the microbial communities. The phylogenetic affiliations of the bands of DGGE were 99 % similar to Clostridium sp.

Bioconversion of Cellulose Into Hydrogen, Biogas and Organic Acids Using Microbial Consortium From a Pulp and Paper Mill Wastewater Treatment Plant

“…Additionally, high substrate concentration could increase a partial pressure in the fermentation reactor, modifying the metabolic pathway to solventogenesis. 30 It was, also, observed in this study; that the ethanol productions in C1, C2 and C3 were of 43.4, 31.8 and 49.9 mg L -1 , indicating a deviation of the metabolic route to solventogenesis and consequently decreasing the hydrogen production in C3.…”

“…30 Moreover, cellulases are relatively costly enzymes, thus its application is an economic disadvantage to the bioenergy technology. In this study, the commercial cellulase application was not needed because the microbial consortia from the WWTP had their own cellulolytic enzyme system.…”

Bacterial communities in thermophilic H2-producing reactors investigated using 16S rRNA 454 pyrosequencing

“…The hydrogen content in the biogas was determined by gas chromatography (GC) using a GC 2010 Shimadzu system (Maintinguer et al 2011;Ratti et al 2013Ratti et al , 2014. The concentrations of organic compounds, such as volatile acids and alcohols, in the liquid phase were determined by high-performance liquid chromatography (HPLC) (Penteado et al 2013).…”

“…The cumulative hydrogen production (H) data were fitted to the modified Gompertz model (Eq. (1)), which is suitable for describing the cumulative biogas production in batch experiments (Ratti et al 2013(Ratti et al , 2014. In this equation, H represents the hydrogen evolution data, t is the period of incubation (h), P is the hydrogen production potential (mmol), R m is the maximum hydrogen production rate (mmol/h), is the length of the lag phase (h) and e is 2.71.…”

“…(2) and (3). Theoretically, 4 mol and 2 mol of H 2 are produced from 1 mol of glucose when acetate and butyrate are the main fermentation products, respectively (Ratti et al 2014;Santos et al 2014).…”