Citrate Supplementation Modulates Medium Viscosity and Poly-γ-Glutamic Acid Synthesis by Engineered 168.

The industrially attractive biopolymer poly-γ-glutamic acid (γ-PGA) is commonly produced by species of the genus by co-feeding different carbon- and nitrogen-sources. Recent studies have highlighted the pivotal role of co-metabolization of a rapidly degradable carbon source such as glycerol together with citrate for γ-PGA production, independently fueling biomass generation as well as tricarboxylic acid (TCA) cycle precursor supply. With this study, we report that the sole presence of citrate in the production medium greatly influences growth behavior, γ-PGA production, and the viscosity of microbial cultures during biopolymer synthesis.

Evaluating microbial contaminations of alternative heating oils.

Since 2008, European and German legislative initiatives for climate protection and reduced dependency on fossil resources led to the introduction of biofuels as CO-reduced alternatives in the heating oil sector. In the case of biodiesel, customers were confronted with accelerated microbial contaminations during storage. Since then, other fuel alternatives, like hydrogenated vegetable oils (HVOs), gas-to-liquid (GtL) products, or oxymethylene ether (OME) have been developed.

Assessment of microbial activity by CO production during heating oil storage.

Microbial activity is the driving force of the carbon cycle, including the digestion of biomass in the soil, oceans, and oil deposits. This natural diversity of microbial carbon sources poses challenges for humans. Contamination monitoring can be difficult in oil tanks and similar settings.

Evaluation of pyruvate decarboxylase-negative strains for the production of succinic acid.

Dicarboxylic acids are important bio-based building blocks, and is postulated to be an advantageous host for their fermentative production. Here, we engineered a pyruvate decarboxylase-negative strain for succinic acid production to exploit its promising properties, that is, lack of ethanol production and accumulation of the precursor pyruvate. The metabolic engineering steps included genomic integration of a biosynthesis pathway based on the reductive branch of the tricarboxylic acid cycle and a dicarboxylic acid transporter.