Alcaligenes eutrophus A5 catabolizes biphenyl to CO2 via benzoate and 4-chlorobiphenyl to 4-chlorobenzoate. In curing and conjugation experiments, the A5 endogenous 51-kb IncP1 plasmid pSS50 was found to be dispensable for biphenyl and 4-chlorobiphenyl catabolism. Transfer of the biphenyl-and 4-chlorobiphenyldegrading phenotype by means of pSS50 was observed at a frequency of 10-5 per transferred plasmid in matings of A5 with other A. eutrophus strains. Transconjugants harbor enlarged pSS50 derivatives which contain additional genetic information governing the oxidation of biphenyl and 4-chlorobiphenyl to benzoate and 4-chlorobenzoate and originating from the chromosome of strain A5. Genes encoding enzymes that degrade polychlorinated biphenyls (PCBs) have been found on both bacterial chromosomes and plasmids. The molecular cloning of chromosomal genes involved in PCB metabolism has been reported previously (1,8,10,17,18). The genetic basis of plasmidmediated degradation has yet to be developed (9,14,29), and this genetic basis may provide information on how such catabolic pathways evolved and spread in the environment (22).Alcaligenes eutrophus A5 was isolated from PCB-contaminated river sediment at Fort Loundoun Reservoir, Knoxville, Tenn., for its ability to utilize 4-chlorobiphenyl (4CBP) as a growth substrate (29). A5 catabolizes 4CBP to 4-chlorobenzoate (4CBA) and biphenyl (BP) to CO2 via benzoate (BA). The appearance of a yellow cleavage intermediate (A437) during 4CBP and BP degradation (31) suggests that A5 metabolizes 4CBP and BP to 4CBA and BA via the catabolic pathway described by Furukawa et al., which includes metacleavage of a 2,3-dihydroxybiphenyl compound (Fig. 1) (11). Strain A5 carries the 51-kb large IncP1 plasmid pSS50, whose characteristics and restriction map are described elsewhere (2,14,19). pSS50 is a remnant of a 75-kb plasmid which lost a 4-CBA dehalogenase activity converting the compound top-hydroxybenzoate and originally enabling A5 to mineralize 4CBP to CO2 (19).So far, it is not clear whether pSS50 still plays a role in the catabolism of 4CBP and BP to 4CBA and BA. We found that transfer of the ability to use 4CBP and BP as the sole sources of carbon and energy (Bph+ Cbp+) from A5 to other A. eutrophus strains occurred at a low frequency and was accompanied by the appearance of an enlarged pSS50 plasmid in the transconjugants (32). The present article reports the genetic analysis of these enlarged pSS50 derivatives and shows that the genes involved in the degradation of BP and * Corresponding author.4CBP to BA and 4CBA in A5 are carried on a chromosomally located element which is able to transpose on pSS50 and other plasmids. MATERIALS AND METHODSBacterial strains, plasmids, and culture media. Bacterial strains and plasmids used in this study and their characteristics are listed in Table 1 All strains were grown at 30°C in Tris minimal medium (21) supplemented with the appropriate carbon source (gluconate or lactate, 0.5%, wt/vol). BP and 4CBP were added as crystals to the lid of...

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Alkaligenes eutrophus strains exhibiting both plasmid-borne heavy metal resistance and haloaromaticdegrading functions were obtained by intraspecific conjugation. The strains which we constructed expressed catabolic and resistance markers together. Degradation of various polychlorinated biphenyl isomers and 2,4-D (2,4-dichlorophenoxyacetic acid) was observed in the presence of 1 mM nickel or 2 mM zinc, provided that the metal resistance determinant was present in the catabolizing strain. Such strains may be useful for decontamination of sites that are polluted with both organic compounds and heavy metals.

A successful transition towards a cleaner and more sustainable energy management in 2050 requires the implementation of renewable energy sources on a large scale. Therefore, it is expected that the share of renewable energy will further increase. Due to the introduction of these intermittent energy sources, the need for flexibility in our energy system increases significantly. Power-togas (P2G) is one promising option for providing long term energy storage and for providing flexibility to the electricity system. An interesting, recent technological development is biological methanation. The latter utilizes microorganisms to catalyze the Sabatier reaction. This biological reaction can be achieved at lower temperatures and pressures than when a chemical catalyst is used and has a higher tolerance to contaminations from the CO2 source, process upset or contamination by foreign organisms. We investigate the techno-economic potential of biological methanation (i.e. microbial power-togas concept) using a case study that revolves around anaerobic digestion using mainly municipal organic waste in Belgium. The most important parameters that influence the economic feasibility are the electricity consumption (44 %), operating hours of the electrolyser (14 %), and the investment cost of the electrolyser (14 %). Based on our findings we offer further routes of research that serve to strengthen the business case.

Wet preservation of algae allows us to bridge the time period between algae harvest and processing while avoiding the costs and nutritional losses associated with algae drying. This study aimed to identify suitable storage conditions for the wet preservation of Nannochloropsis gaditana concentrates. The impact of storage temperature, time and the way of closing the storage recipient was evaluated using a full factorial design. The effect of acetic acid addition was tested for one storage condition. Storage temperature was the main factor determining the microbial count and had a vast impact on the formation of odorous metabolites. Storage at 20 °C in closed recipients led to rapid O2 consumption, accumulation of malodorous short-chain fatty acids above their odor thresholds, and the production of H2S and methanethiol. These odorous metabolites were not formed or to a much lower extent during 4 °C and 8 °C storage in closed recipients. Acetic acid supplementation (50 mM) suppressed the formation of short-chain fatty acids during 8 °C storage in unsealed recipients and reduced the aerobic microbial count and the number of yeasts and molds by approximately one log unit after 14 days. Yet, acetic acid addition also induced lipid hydrolysis and decreased chlorophyll levels when algae were stored for more than one week. This study demonstrated that temperature control is needed and that acetic acid addition is a promising approach when N. gaditana concentrates are stored for less than one week.