Eight Up-Coming Biotech Tools to Combat Climate Crisis.

Biotechnology has a high potential to substantially contribute to a low-carbon society. Several green processes are already well established, utilizing the unique capacity of living cells or their instruments. Beyond that, the authors believe that there are new biotechnological procedures in the pipeline which have the momentum to add to this ongoing change in our economy. Eight promising biotechnology tools were selected by the authors as potentially impactful game changers: (i) the Wood-Ljungdahl pathway, (ii) carbonic anhydrase, (iii) cutinase, (iv) methanogens, (v) electro-microbiology, (vi) hydrogenase, (vii) cellulosome and, (viii) nitrogenase. Some of them are fairly new and are explored predominantly in science labs. Others have been around for decades, however, with new scientific groundwork that may rigorously expand their roles. In the current paper, the authors summarize the latest state of research on these eight selected tools and the status of their practical implementation. We bring forward our arguments on why we consider these processes real game changers.

Anaerobic Digestion of Pretreated Industrial Residues and Their Energetic Process Integration.

The food and beverage industry offers a wide range of organic feedstocks for use in biogas production by means of anaerobic digestion (AD). Microorganisms convert organic compounds-solid, pasty, or liquid ones-within four steps to biogas mainly consisting of CH4 and CO2. Therefore, various conversion technologies are available with several examples worldwide to show for the successful implementation of biogas technologies on site. The food and beverage industry offer a huge potential for biogas technologies due to the sheer amount of process residues and their concurrent requirement for heat and power. The following study analyzes specific industries with respect to their implementation potential based on arising waste and heat and power demand. Due to their chemical composition, several feedstocks are resistant against microbiological degradation to a great extent. A combination of physical-, chemical-, and microbiological pretreatment are used to increase the biological availability of the feedstock. The following examples will discuss how to best implement AD technology in industrial processes. The brewery industry, dairy production, slaughterhouses, and sugar industry will serve as examples.

Optimisation of continuous gas fermentation by immobilisation of acetate-producing Acetobacterium woodii.

Hydrogen from water electrolysis is often suggested as a way of storing the excess energy from wind and solar power plants. However, unlike natural gas, hydrogen is difficult to store and distribute. One solution is to convert the hydrogen into other fuels or bulk chemicals. In this study we investigated fermentation in which homoacetogenic clostridia apply the Wood-Ljungdahl pathway to generate acetate from H2 and CO2. Acetate can be used as a bulk chemical or further transformed into biofuels. Autotrophic growth with CO2 as the sole carbon source is slow compared to heterotrophic growth, so the aim of this work was to improve continuous gas fermentation by immobilising the acetate-producing clostridia, thus preventing their wash out from the bioreactor. Two homoacetogenic bacterial strains (Acetobacterium woodii and Moorella thermoacetica) were tested for their acetate production potential, with A. woodii proving to be the better strain with maximum acetate concentration of 29.57 g l-1. Due to its stability during fermentation and good bacterial immobilisation, linen was chosen as immobilisation material for continuous fermentation. This study demonstrates the successful continuous fermentation of acetate from H2 and CO2 using A. woodii immobilised on a low-cost surface at high volumetric productivity of 1.21 ± 0.05 g acetate l-1 d-1. This has great industrial potential and future studies should focus on the scale-up of this process.

Characteristics of adapted hydrogenotrophic community during biomethanation.

The results presented in this study were carried out as concomitant experiments during the start-up and operation of a biomethanation unit to evaluate the effect of process parameters on carbon conversion, product formation (methane and acetate) and community composition. For that, two different samples were withdrawn from a trickle-bed reactor with immobilized enrichment culture of hydrogenotrophic methanogens adapted from sewage sludge. One sample was taken from the recirculation liquid during start-up phase while the other was withdrawn directly from the carrier material in the reactor. Elevated acid levels especially during start-up were shown to affect the overall carbon conversion. This effect was also seen during the acid tolerance testing reported here. Final acid concentrations of 1.6±0.3g/L resulted in a reduced conversion ratio of only 46%. Without acid addition complete conversion of CO2 in the headspace was achieved. However, maximum methane production of 0.55±0.02mmol after 4days of incubation was monitored at moderate initial acetate concentration of 0.4g/L. In both analyzed inoculation materials Methanobacterium species were by far the most dominant Archaea with 21.8% in the recirculation liquid during start-up and 84.8% in the enrichment culture immobilized on the carrier material. The microbial composition of the two analyzed samples is in accordance with the results obtained for the carbon conversion and product formation. With approximately 50% of Bacteroidetes and Firmicutes present during reactor start-up the acetic acid production significantly contributed to the overall carbon conversion. In contrast, methane was produced almost exclusively in trials representing continuous operation where acetogenic bacteria accounted only up to 17.5%. In summary, the acid accumulation monitored during reactor start-up of a biomethanation unit is most likely to result from the microbial composition present. Nevertheless, complete adaptation to hydrogenotrophic conditions was proven to alter the consortium and yield methane as main product alongside high carbon conversion of up to 70.5±1.8%.