Bioaugmentation potential of inoculum derived from anaerobic digestion feedstock for enhanced methane production using water hyacinth.

The utilisation of water hyacinth for production of biogas is considered to be a solution to both its control and the global renewable energy challenge. In this instance, an investigation was conducted to evaluate the potential of water hyacinth inoculum to enhance methane production during anaerobic digestion (AD). Chopped whole water hyacinth (10% (w/v)) was digested to prepare an inoculum consisting mainly of water hyacinth indigenous microbes. The inoculum was incorporated in the AD of freshly chopped whole water hyacinth to set up different ratios of water hyacinth inoculum and water hyacinth mixture with appropriate controls. The results of batch tests with water hyacinth inoculum showed a maximal cumulative volume of 211.67 ml of methane after 29 days of AD as opposed to 88.6 ml of methane generated from the control treatment without inoculum. In addition to improving methane production, inclusion of water hyacinth inoculum reduced the electrical conductivity (EC) values of the resultant digestate, and, amplification of nifH and phoD genes in the digestate accentuates it as a potential soil ameliorant. This study provides an insight into the potential of water hyacinth inoculum to enhance methane production and contribute to the feasibility of the digestate as a soil fertility enhancer.

Carbon flow, energy metabolic intensity and metagenomic characteristics of a Fe (III)-enhanced anerobic digestion system during treating swine wastewater.

Deep treatment and bioenergy recovery of swine wastewater (SW) are beneficial for constructing a low-carbon footprint and resource-recycling society. In this study, Fe (III) addition from 0 to 600 mg/L significantly increased the methane (CH4) content of the recovered biogas from 61.4 ± 2.0 to 89.3 ± 2.0 % during SW treatment in an anaerobic membrane digestion system. The specific methane yields (SMY) also increased significantly from 0.20 ± 0.05 to 0.29 ± 0.02 L/g COD. Fe (III) and its bio-transformed products which participated in establishing direct interspecific electron transfer (DIET), upregulated the abundance of e-pili and Nicotinamide adenine dinucleotide (NADH), enriched electroactive bacteria. The increase in cellular adenosine triphosphate (cATP) from 6583 to 14,518 ng/gVSS and electron transport system (ETS) from 1468 to 1968 mg/(g·h) promoted the intensity of energy flow and electron flow during anaerobic digestion of SW. Moreover, Fe (III) promoted the hydrolysis and acidification of organic matters, and strengthened the acetoacetic methanogenesis pathway. This study established an approach for harvesting high quality bioenergy from SW and revealed the effects and mechanisms from the view of carbon flow, energy metabolic intensity and metagenomics.

Whole genome sequence of Serratia marcescens 39_H1, a potential hydrolytic and acidogenic strain.

Here, we report a high quality annotated draft genome of Serratia marcescens 39_H1, a Gram-negative facultative anaerobe that was isolated from an anaerobic digester. The strain exhibited hydrolytic/acidogenic properties by significantly improving methane production when used as a single isolate inoculum during anaerobic digestion of water hyacinth and cow dung. The total genome size of the isolate was 5,106,712 bp which corresponds to an N50 of 267,528 and G + C content of 59.7 %. Genome annotation with the NCBI Prokaryotic Genome Annotation Pipeline (PGAP) predicted a total of 4,908 genes of which 4,755 were protein coding genes; there were no plasmids detected. A number of genes associated with hydrolytic/acidogenic activities as well as other metabolic activities were identified and discussed.

Isolation and characterisation of crude oil sludge degrading bacteria.

BACKGROUND: The use of microorganisms in remediating environmental contaminants such as crude oil sludge has become a promising technique owing to its economy and the fact it is environmentally friendly. Polycyclic aromatic hydrocarbons (PAHs), as the major components of oil sludge, are hydrophobic and recalcitrant. An important way of enhancing the rate of PAH desorption is to compost crude oil sludge by incorporating commercial surfactants, thereby making them available for microbial degradation. In this study, crude oil sludge was composted for 16 weeks during which surfactants were added in the form of a solution. RESULTS: Molecular characterisation of the 16S rRNA genes indicated that the isolates obtained on a mineral salts medium belonged to different genera, including Stenotrophmonas, Pseudomonas, Bordetella, Brucella, Bacillus, Achromobacter, Ochrobactrum, Advenella, Mycobacterium, Mesorhizobium, Klebsiella, Pusillimonas and Raoultella. The percentage degradation rates of these isolates were estimated by measuring the absorbance of the 2,6-dichlorophenol indophenol medium. Pseudomonas emerged as the top degrader with an estimated percentage degradation rate of 73.7% after 7 days of incubation at 28 °C. In addition, the presence of the catabolic gene, catechol-2,3-dioxygenase was detected in the bacteria isolates as well as in evolutionary classifications based on phylogeny. CONCLUSIONS: The bacteria isolated in this study are potential agents for the bioremediation of crude oil sludge.