Phaeobacter inhibens DSM 17395, a model organism for marine Roseobacter group, was studied for its response to its own antimicrobial compound tropodithietic acid (TDA). TDA biosynthesis is encoded on the largest extrachromosomal element of P. inhibens, the 262 kb plasmid, whose curation leads to an increased growth and biomass yield. In this study, the plasmid-cured strain was compared to the wild-type strain and to transposon mutants lacking single genes of the TDA biosynthesis. The data show that the growth inhibition of the wild-type strain can be mainly attributed to the TDA produced by P. inhibens itself. Oxygen uptake rates remained constant in all strains but the growth rate dropped in the wild-type which supports the recently proposed mode of TDA action. Metabolome analysis showed no metabolic alterations that could be attributed directly to TDA. Taken together, the growth of P. inhibens is limited by its own antibacterial compound due to a partial destruction of the proton gradient which leads to a higher energetic demand. The universal presence of TDA biosynthesis in genome-sequenced isolates of the genus Phaeobacter shows that there must be a high benefit of TDA for P. inhibens in its ecological niche despite the drawback on its metabolism.

The concept of the microbial fuel cell (MFC) has existed for over 100 years, but only within the last decade, the practical implementation has become conceivable due to microbial and technical progress. This review article presents available strategies to increase the limiting extracellular electron transfer (EET) in the anode space of MFCs. Therefore, organism‐based improvements as well as the effects of (bio–)polymers and redox mediators on ETT will be demonstrated.

The advances in bioprocess design, genetic engineering, and media optimization have enabled enhanced bacterial cellulose (BC) production and its application for diverse purposes. Following the requirements of a bioeconomy, numerous approaches were conducted to investigate alternative carbon or nitrogen sources from industrial by-products for BC biosynthesis. They can, however, not only affect the BC production but also its properties. Beet molasses, vinasse, and waste beer fermentation broth (WBFB) have thus been investigated in single and combined approaches for their BC production potential and effects on structural properties using Komagataeibacter xylinus DSM 2325. Therefore, the composition of each complex component was initially analyzed for total organic carbon (TOC), total bound nitrogen (TNb), sugars, organic acids, and alcohols. The polymer properties were characterized via gel permeation chromatography and X-ray diffraction. In dynamic shake flask cultivations, the exchange of Hestrin-Schramm (HS) medium components for a combination of all three complex substrates on a TOC- or TNb-based quantity resulted in the highest BC concentration (8.2 g L−1). Comparable concentrations were achieved when combining molasses and WBFB (8.1 g L−1). Each investigated complex component led to differing degrees of polymerization (DPn: 2751−4601) and BC crystallinities (26−58%) in comparison to HS medium. Beet molasses and vinasse were found to decrease the polymer crystallinity but induce higher DPn whereas the opposite occurred for WBFB. This study thus highlights beneficial effects of food industry by-products for BC biosynthesis and elucidates concomitantly occurring structural polymer alterations to enable further studies dealing with alternative substrates for structurally tailored BC production.

The need for energy-storing technologies with lower environmental impact than Li-ion batteries but similar power metrics has revived research in Zn-based battery chemistries. The application of bio-based materials as a replacement for current components can additionally contribute to an improved sustainability of Zn battery systems. For that reason, bacterial cellulose (BC) was investigated as separator material in Ni-Zn batteries. Following the biotechnological production of BC, the biopolymer was purified, and differently shaped separators were generated while surveying the alterations of its crystalline structure via X-ray diffraction measurements during the whole manufacturing process. A decrease in crystallinity and a partial change of the BC crystal allomorph type Iα to II was determined upon soaking in electrolyte. Electrolyte uptake was found to be accompanied by dimensional shrinkage and swelling, which was associated with partial decrystallization and hydration of the amorphous content. The separator selectivity for hydroxide and zincate ions was higher for BC-based separators compared to commercial glass-fiber (GF) or polyolefin separators as estimated from the obtained diffusion coefficients. Electrochemical cycling showed good C-rate capability of cells based on BC and GF separators, whereas cell aging was pronounced in both cases due to Zn migration and anode passivation. Lower electrolyte retention was concluded as major reason for faster capacity fading due to zincate supersaturation within the BC separator. However, combining a dense BC separator with low zincate permeability with a porous one as electrolyte reservoir reduced ZnO accumulation within the separator and improved cycling stability, hence showing potentials for separator adjustment.

Das Konzept der mikrobiellen Brennstoffzelle (microbial fuel cell, MFC) existiert seit über 100 Jahren, doch erst im letzten Jahrzehnt ist deren praktische Anwendung in der Abwasseraufbereitung auch in Maßstäben bis 1000 L realisiert worden. In diesem Beitrag werden verfügbare Strategien vorgestellt, um den bislang noch limitierenden extrazellulären Elektronentransfer (EET) im Anodenraum von MFCs zu erhöhen. Dafür werden Organismen-basierte Ansätze sowie der Einfluss von (Bio-)Polymeren und Redox-Mediatoren auf den EET vorgestellt.The concept of the microbial fuel cell (MFC) has existed for over 100 years, but only since the last decade its practical implementation in waste water treatment has been realized in scales up to 1000 L. This review article shows available strategies to increase the limiting extracellular electron transfer (EET) for anode space of MFCs. Therefore, organism-based improvements as well as the effect of (bio)polymers and redox mediators on ETT will be demonstrated.