A high gas fraction, reduced power, syngas bioprocessing method demonstrated with a Clostridium ljungdahlii OTA1 paper biocomposite

Abstract

We propose a novel approach to continuous bioprocessing of gases. A miniaturized coated-paper high gas fraction biocomposite absorber has been developed using slowly shaken horizontal anaerobic tubes with concentrated Clostridium ljungdahlii OTA1 absorbing syngas as a model system. These gas absorbers demonstrate elevated CO mass transfer with low power input, reduced liquid requirements, elevated substrate consumption, and increased product secretion compared to shaken suspended cells. We concentrate OTA1 in a cell paste which was coated by extrusion onto chromatography paper. Cell adhesion was by adsorption to the cellulose fibers; visualized by SEM. The C. ljungdahlii OTA1 coated paper mounted above the liquid level absorbs CO and H2 from a model syngas producing acetate with minimal ethanol. At 100 rpm shaking speed (7.7 W m−3) the optimal cell loading is 6.5 gDCW m−2 to maintain high CO absorbing reactivity without the cells coming off of the paper into the liquid phase. Reducing the medium volume from 10 mL to 4 mL (15% of tube volume) did not decrease CO reactivity. The reduced liquid volume increased secreted product concentration by 80%. The specific CO consumption by paper biocomposites was higher at all shaking frequencies <100 rpm than suspended cells under identical incubation conditions. At 25 rpm the biocomposite outperforms suspended cells for CO absorption by 2.5 fold, with a power reduction of 97% over the power input at 100 rpm. The estimated minimum apparent kLa for these biocomposite gas-absorbers is ~100 h−1, a 10 to 104 less power input than other syngas fermentation systems at similar kLa. Specific consumption rates in a biocomposite were measured as ~14 mmol gDCW−1 h−1. This work intensified CO absorption and reactivity by 14 fold to 94 mmol CO m−2 h−1 over previous C. ljungdahlii OTA1 work by our group. Specific acetate production rates were 23 mM h−1 or 46 mmol m−2 h−1. The specific rates and apparent kLa were shown to scale linearly with biocomposite coating area. These proof of concept results will be used to engineer a continuous biocomposite gas absorber bioreactor.

Using gas mixtures of CO, CO2 and H2 as microbial substrates: the do's and don'ts of successful technology transfer from laboratory to production scale

“…Very few studies have been reported so far on the application of trickle-bed reactors for syngas fermentation on a laboratory-scale (e.g. Bredwell et al, 1999;Yasin et al, 2015;Devarapalli et al, 2016;Schulte et al, 2016;Shen et al, 2017). High CO conversion rates of up to 91% were observed with Clostridium ragsdalei in a trickle-bed reactor with non-porous glass beads of 6 mm as carriers (Devarapalli et al, 2016).…”

Biocoatings: A new challenge for environmental biotechnology

“…Some common biocoating deposition techniques include extrusion [34,90,91], spray drying [92], the wire wound rod drawdown Mayer rod coating method [13,67,93], 3-D ink-jet deposition [94] and the convective assembly [12,47,95]. Recently, dielectrophoresis (DEP) has also been used to generate photoreactive cyanobacteria cell monolayers on top of polyelectrolyte adhesives [96].…”

“…PCC7002 (cyanobacterial aerobic phototroph). Investigation of C. ljungdahlii biocoated papers, coated without adhesive latex, has recently be extended by Schulte et al [91], who optimized surface area, with mass-transfer power input reduced by 3 orders of magnitude compared to traditional bioreactors and reduced liquid volume. His approach intensified the rate of CO uptake by over 17 fold.…”

A technique for lyopreservation of Clostridium ljungdahlii in a biocomposite matrix for CO absorption

“…Stabilization of anaerobic bacteria that are capable of assimilating single carbon gases, such as C . ljungdahlii , and other clostridia, could prove to be highly beneficial in developing bioprocess-oriented large scale gas treatment technologies [ 5 – 7 ].…”

“…In this study, a thin-film coating based approach of embedding the microbial samples in paper based biocomposite was undertaken [ 5 , 20 ], and a simple convective drying mechanism using inert argon gas purge technique was used for dry-processing the samples. The technique employed here is significantly different and simpler from the conventional drying modalities commonly used in the bioprocessing industry such as lyophilization and spray drying.…”