A large collection of bacterial strains, immunotrapped from soil and from the wheat rhizoplane, was subjected to polyphasic taxonomy by examining various pheno-and genotypic parameters. Strains were grouped on (inter) repetitive extragenic palindromic DNA (REP) PCR profiles at the intraspecies level. Pheno-and genotypic characters were assessed for representatives from 13 different REP groups. Strains of nine REP groups constituting two physiological BIOLOG clusters fell in the coherent DNA-DNA reassociation group of Ochrobactrum anthropi. Strains of two REP groups constituting a separate BIOLOG cluster fell in the coherent DNA-DNA reassociation group of Ochrobactrum intermedium. Additional phenotypic characters differentiating O. anthropi and O. intermedium were found. REP group K strains constituted a different BIOLOG cluster, a separate DNA-DNA reassociation group and a distinct phylogenetic lineage in 16S rDNA homology analysis, indicating that REP group K strains represent a new species. Diagnostic phenotypic characters were found. Closest relatives were Ochrobactrum species. The name Ochrobactrum grignonense sp. nov. is proposed (type strain OgA9a T l LMG 18954 T l DSM 13338 T ). REP group J strains again constituted a different BIOLOG cluster, a separate DNA-DNA reassociation group and showed, as a biological particularity, a strict preference for the rhizoplane as habitat. Diagnostic phenotypic characters were found. This indicated that REP group J strains represent a further new species, although phylogenetic analyses using 16S rDNA homology were not able to separate the cluster of REP group J sequences significantly from 16S rDNA sequences of Ochrobactrum anthropi. The name Ochrobactrum tritici sp. nov. is proposed (type strain SCII24 T l LMG 18957 T l DSM 13340 T ).

Worldwide, anaerobic digestion for sanitation and utilization of the produced biogas as energy carrier have a long-standing history. Concomitantly, digested residues from biogas plants are utilized as valuable fertilizers in crop production. In Germany, guaranteed prices for electricity generated from renewable sources pushed the number of biogas plants from about 140 in 1992 to about 7,720 by the end of 2013, and the share of electricity supply from biogas close to 4.5%. In the midterm, biogas is given considerable potential to fill up the residual load from electricity generation based on wind and photovoltaic. In this review, we give an overview of the state-of-the-art of biogas technology for energy supply from agricultural inputs, based mainly on the situation in Germany. Focus is placed on the monitoring and control (M&C) of biogas plants as a means of meeting the growing demands for productivity and reliability of biogas supply. We summarize prominent factors for the stability and productivity of the anaerobic digestion (AD) process, and present latest findings about molecular biology tools, bioindicators, the 'metabolic quotient' and cDNA/DNA ratios for process analysis. In view of the large diversity of agricultural biogas installations, we discuss the cost-benefit ratio of M&C effort and equipment. In the light of the transformation of the energy system in Germany towards renewable sources ('Energiewende'), we give an outlook on prospects and concepts for the future role of biogas technology in agriculture and energy supply. We also address recent misguided developments, as the sustainable development of biogas technology in agriculture can only be realized within the ecological, economical, and social boundaries of underlying agro-ecological systems.Keywords: Agriculture; Biogas production; Process control; Engineering; Microbiology; Molecular biology; Early-warning; Energy supply on demand ReviewThe most prominent beneficial features of the anaerobic digestion (AD) process are generation of biogas as a renewable energy carrier based on solar energy stored in biomass and hygienization of the input material during the treatment. Although it turns out from the following section that making use of hygienization is invaluable and has a long-standing history, the focus of this manuscript is on energy supply from biogas. The intent is to highlight the role of biogas production in a sustainable renewable energy framework in order to counteract consequences of the unsustainable resource management in the last century. Moreover, intensifying sustainable energy use has gained particular importance since the recent catastrophes with nuclear energy.This article builds on recent reviews by Weiland [1] and Braun et al. [2] on the state of biogas production in 2010, with emphasis on the development in Germany. In the last few years, the role of biogas as envisaged in the German renewable energy concept (see 'The role of biogas within the German energy supply system' section) has fuelled respective research a...

Biogas production from mono-digestion of maize silage was studied for more than one year in six continuously stirred, daily fed 36 L fermenters. Chemical and microbiological parameters were analysed concomitantly. The reactors acidified already after 8 months of operation at a low organic loading rate (OLR) of 2 g VS*(L*d)(-1). The TVA/TAC ratio was the most reliable parameter to indicate early process instabilities leading to acidification. A TVA/TAC threshold of 0.5 should not be exceeded. After acidification and recovery of the fermenters, propionic acid was no reliable parameter anymore to indicate process failure, since values far below the threshold of 1 g*L(-1) were obtained although the process had collapsed.The acidified reactors recovered better, showed greatly improved stability and allowed a higher OLR when a trace element (TE) cocktail was supplemented. Hydrolysis was obviously not process-limiting, results indicated that methanogens were affected. The most limiting element in long-term mono-digestion of maize silage turned out to be cobalt, but data obtained suggest that molybdenum and selenium should also be provided. TE supplementation should be designed specifically in order to meet the actual needs. TE availability for the biocenosis appears to be a key issue in biogas production, not only in mono-but also in co-digestion processes.

We determined the actual (no tryptophan, Trp, addition) and potential (Trp 0.1 g l−1 added) production of indolic and phenolic compounds produced in different culture media by Paenibacillus polymyxa strains which had been isolated from different proximity to wheat roots. The production of indole‐3‐acetic acid (IAA) and related indolic metabolites by all strains tested was greatly enhanced upon Trp addition, suggesting that Trp is important as IAA precursor. A gradual decrease in potential IAA and an increase in potential indole‐3‐ethanol and indole‐3‐lactic acid production by strains isolated from non‐rhizosphere soil (NRS) over rhizosphere soil (RS) to the rhizoplane (RP) were obtained. The NRS strain showed also a higher (potential) production of oxidized compounds such as indole‐3‐carboxylic and benzoic acid besides IAA. The determined metabolic differences indicate together with previous results on genetic and physiological parameters of P. polymyxa populations that plant roots select different P. polymyxa subpopulations. Our results suggest that the selected genotypes are differentially adapted to the decreasing oxygen pressure from NRS to RP. Possible effects of the probably microhabitat‐specific metabolic profiles of the P. polymyxa isolates for plant growth are discussed.

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