No abstract

Bio‐based carboxylic acids are promising platform chemicals. State‐of‐the‐art fermentations produce salts of carboxylic acids at neutral pH. Downstream processing of these fermentation broths traditionally involves a pH shift producing waste salts. These waste salts reduce the sustainability and economics of bio‐cased carboxylic acid production. Waste salt production can be avoided by inducing the pH shift electrochemically. Experimental feasibility studies of an electrochemical downstream process and investigations of electrochemically induced nucleation and crystal growth are given. The presented electrochemical downstream concept enables in situ production of succinic acid and simultaneous pH management of pH neutral fermentations without the side production of waste salts.

Biotechnological production of platform chemicals such as (di)­carboxylic acids poses economic and environmental challenges in downstream processing. With conventional downstream processes, waste salts are produced in more than equimolar amounts with the product. Therefore, lean waste-free downstream processes are needed to compete with petrochemical products. This work presents a joint development of a biobased production route for itaconic acid featuring low pH value fermentation, reactive extraction, and electrochemical product recovery. By the implementation of an electrochemical pH-T-swing separation process, biobased itaconic acid with a purity of more than 99% was recovered in the crystalline form from the fermentation broth. Based on the measured liquid–liquid and solid–liquid equilibrium, a feasible overall yield of >90% for itaconic acid recovery was calculated for the proposed downstream process. An electrochemical protonation efficiency of 96.2% was determined when the pH-shift electrolysis operates within the buffer range of the itaconic acid. The proposed process eliminates the salt waste from pH-adjusting steps and can perspectively operate with electricity costs being lower than costs for sulfuric acid and sodium hydroxide elsewise required for the pH-swing steps.

Electrified downstream processes for biotechnologically produced carboxylic acids reduce waste salt generation significantly and make biotechnological production ecologically and economically more attractive. In order to design, optimize, scale-up and control electrochemically induced crystallization processes, knowledge of the metastable zone width (MSZW) is essential. An optical observation approach of nucleation processes close to the electrode and determination of the MSZW is presented. This work presents a method for MSZW measurements for electrochemically induced pH-shift crystallization processes by monitoring the nucleation, the saturation pH value and saturation concentration for different current densities. The measured MSZWs for electrochemically induced pH-shift crystallization are narrow due to the foreign surface, gas bubbles and electrode surface, and rising current densities lead to even smaller MSZW. Nucleation parameters are estimated from MSWZ data, adapting the classical approach of Nývlt to electrochemically induced crystallization.

The production of large scaffold‐free tissues is a key challenge in regenerative medicine. Nowadays, temperature‐responsive polymers allow intact tissue harvesting without needing proteolytic enzymes. This method is limited to tissue culture plastic with limited upscaling capacity and plain process control. Here, a thermoresponsive hollow fiber membrane bioreactor is presented to produce large scaffold‐free tissues. Intact tissues, rich in cell‐to‐cell connections and ECM, are harvested from a poly(N‐vinylcaprolactam) microgel functionalized poly(ether sulfone)/poly(vinylpyrrolidone) hollow fiber membrane by a temperature shift. The harvested 3D tissues adhere in successive cultivation and exhibit high vitality for several days. The facile adsorptive coating waives the need for extensive surface treatment. The research is anticipated to be a starting point for upscaling the production of interconnected tissues enabling new opportunities in regenerative medicine, large‐scale drug screening on physiological relevant tissues, and potentially opening new chances in cell‐based therapies.