Carbon monoxide fermentation to bioplastic: the effect of substrate adaptation on Rhodospirillum rubrum

AbstractRhodospirillum rubrum is a gram-negative bacterium that naturally takes advantage of CO and which, in the presence of acetate, accumulates carbon and energy units as polyhydroxybutyrate (PHB). Since the conversion of CO depends on a large protein membrane complex that is expressed after the exposure to carbon monoxide, this study presents the effects of a CO-based acclimation in R. rubrum on the growth trend and on the production of PHB. The strain was cultured in two consecutive fermentation cycles on 15% of CO, and the behaviour of this species, in the presence of acetate or a reducing sugar, such as fructose, was compared. The exposure of R. rubrum to CO during the first adaptation phase led to the development of a metabolically active population characterised by a greater biomass growth. The supply of fructose ensured a shorter lag-phase and a higher biomass titre, but it also determined a decrease in the biopolymer accumulation. However, R. rubrum showed the best carbon utilisation in the absence of fructose, with a growth molar yield of 48 mg mol−1, compared to the 12 mg mol−1 obtained for fructose feeding

Biorefarmeries: Milking ethanol from algae for the mobility of tomorrow

The idea of this project is to fully exploit microalgae to the best of its potential, possibly proposing a sort of fourth generation fuel based on a continuous milking of macro- and microorganisms (as cows in a milk farm), which produce fuel by photosynthetic reactions. This project proposes a new transportation concept supported by a new socio-economic approach, in which biofuel production is based on biorefarmeries delivering fourth generation fuels which also have decarbonization capabilities, potential negative CO2 emissions plus positive impacts on mobility, the automotive Industry, health and environment and the econom

Novel insights in dimethyl carbonate-based extraction of polyhydroxybutyrate (PHB)

Background: Plastic plays a crucial role in everyday life of human living, nevertheless it represents an undeniable source of land and water pollution. Polyhydroxybutyrate (PHB) is a bio-based and biodegradable polyester, which can be naturally produced by microorganisms capable of converting and accumulating carbon as intracellular granules. Hence, PHB-producing strains stand out as an alternative source to fossil-derived counterparts. However, the extraction strategy affects the recovery efficiency and the quality of PHB. In this study, PHB was produced by a genetically modified Escherichia coli strain and successively extracted using dimethyl carbonate (DMC) and ethanol as alternative solvent and polishing agent to chloroform and hexane. Eventually, a Life Cycle Assessment (LCA) study was performed for evaluating the environmental and health impact of using DMC. Results: Extraction yield and purity of PHB obtained via DMC, were quantified, and compared with those obtained via chloroform-based extraction. PHB yield values from DMC-based extraction were similar to or higher than those achieved by using chloroform (≥ 67%). To optimize the performance of extraction via DMC, different experimental conditions were tested, varying the biomass state (dry or wet) and the mixing time, in presence or in absence of a paper filter. Among 60, 90, 120 min, the mid-value allowed to achieve high extraction yield, both for dry and wet biomass. Physical and molecular dependence on the biomass state and solvent/antisolvent choice was established. The comparative LCA analysis promoted the application of DMC/ethanol rather than chloroform/hexane, as the best choice in terms of health prevention. However, an elevated impact score was achieved by DMC in the environmentallike categories in contrast with a minor contribution by its counterpart. Conclusion: The multifaceted exploration of DMC-based PHB extraction herein reported extends the knowledge of the variables affecting PHB purification process. This work offers novel and valuable insights into PHB extraction process, including environmental aspects not discussed so far. The findings of our research question the DMC as a green solvent, though also the choice of the antisolvent can influence the impact on the examined categories.This work has been funded by the Horizon 2020 EU Framework Programme: CELBICON project, Grant agreement number: 679050. Open access funding provided by PRIME project funded by the POR FESR 2014/2020 Programme, Asse I – Azione I.1b.2.2 Regione Piemonte, within the Piattaforma Tecnologica per la Bioeconomia.Publicad

Biotechnological approches for green-based bioplastic production

L'abstract è presente nell'allegato / the abstract is in the attachmen

About how to capture and exploit the CO2 surplus that nature, per se, is not capable of fixing

10 p.-2 fig.Human activity has been altering many ecological cycles for decades, disturbing the natural mechanisms which are responsible for re-establishing the normal environmental balances. Probably, the most disrupted of these cycles is the cycle of carbon. In this context, many technologies have been developed for an efficient CO2 removal from the atmosphere. Once captured, it could be stored in large geological formations and other reservoirs like oceans. This strategy could present some environmental and economic problems. Alternately, CO2 can be transformed into carbonates or different added-value products, such as biofuels and bioplastics, recycling CO2 from fossil fuel. Currently different methods are being studied in this field. We classified them into biological, inorganic and hybrid systems for CO2 transformation. To be environmentally compatible, they should be powered by renewable energy sources. Although hybrid systems are still incipient technologies, they have made great advances in the recent years. In this scenario, biotechnology is the spearhead of ambitious strategies to capture CO2 and reduce global warming.Research on polymer biotechnology at the laboratory of Auxiliadora Prieto is supported by grants from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreements, no 633962, no. 679050, no. 745791 and no. 745737. We also acknowledge the Community of Madrid (P2013/MIT2807) and the Spanish Ministry of Economy (BIO2013-44878R, BIO2014- 61515-EXP).Peer reviewe

Maximization of poly(3-hydroxybutyrate) production in fed-batch cultures of A. vinelandii based on the variation of the agitation rate

1. Introduction The poly-hydroxybutyrate (PHB) is a polyethylene-like bioplastic naturally synthetized by several classes of microorganisms, as a source of energy and carbon unit [1]. This material, which is a promising candidate for the replacement of fossil-based plastic, is already present at an industrial scale. However, the maximization of its production process is the goal to achieve in order to reduce production costs. Azotobacter vinelandii is strictly aerobic gram-negative soil bacteria, able to produce PHB in a carbon substrate-rich environment and under oxygen-limitation conditions [2]. The production of this polymer is particularly interesting in this species, because it can accumulate up to 85% of its dried biomass as PHB [3]. It is known that agitation rate affects the PHB production by A. vinelandii [2]. In this work, the PHB productivity under fed-batch cultivation was evaluated to different volumetric oxygen transfer coefficient (kLa). Thus, it was possible to determine an adequate kLa range for scale-up the production of PHB. 2. Methods Batch cultures of Azotobacter vinelandii OP were performed in a 3 L bioreactor (30 g L-1 sucrose as carbon source) at 600 rpm during 30 h. After of this time, the cultures were fed by a single medium feeding pulse of the carbon source and the agitation speed was varied between 400 and 1000 rpm. The biomass evolution and the PHB production were evaluated. The kLa was estimated at different agitation rate using dynamic method. 3. Results and discussion The maximal accumulation of biomass was 13.3 g L-1, obtained at an agitation speed of 800 rpm (Table 1). The highest agitation speed increased the specific growth rate, reaching a value of 0.069 h-1 to 1000 rpm. During fed-batch cultivation, a change in the agitation speed affected the PHB accumulation, obtaining the highest value (79.1 % w w-1) to 600 rpm