Display omitted
► Nitrogen limitation in turbidostats causes a metabolic energy imbalance in microalgae. ► This energy imbalance allows simultaneous cell replication and TAG accumulation. ► ...Neochloris oleoabundans used TAG as an energy sink when exposed to excess light energy. ► Excess light energy was predominantly dissipated rather than stored in TAG.
In this paper the hypothesis was tested whether TAG accumulation serves as an energy sink when microalgae are exposed to an energy imbalance caused by nutrient limitation. In our continuous culture system, excess light absorption and growth-limiting nitrogen supply rates were combined, which resulted in accumulation of TAG (from 1.5% to 12.4% w/w) in visible lipid bodies in Neochloris oleoabundans, while cell replication was sustained. A fourfold increase in TAG productivity showed that TAG indeed served as an energy sink. However, the bulk of excess energy was dissipated leading to a significantly reduced biomass productivity and yield of biomass on light. This demonstrates that when aiming at industrial TAG production, sustaining efficient light energy use under nutrient stress is an important trait to look for in potential production organisms.
Biorefinery of microalgae for food and fuel Vanthoor-Koopmans, Marieke; Wijffels, Rene H.; Barbosa, Maria J. ...
Bioresource technology,
05/2013, Letnik:
135
Journal Article
Recenzirano
Microalgae are a promising source for proteins, lipids and carbohydrates for the food/feed and biofuel industry. In comparison with soya and palm oil, microalgae can be grown in a more efficient and ...sustainable way. To make microalgae production economically feasible it is necessary to optimally use all produced compounds. To accomplish this focus needs to be put on biorefinery techniques which are mild and effective. Of the techniques described, Pulsed Electric Field (PEF) seems to be the most developed technique compared to other cell disruption applications. For separation technology ionic liquids seems most promising as they are able to both separate hydrophobic and hydrophilic compounds. But additional studies need to be evolved in the coming years to investigate their relevance as novel cell disruption and separation methods. We propose a complete downstream processing flow diagram that is promising in terms of low energy use and state of the art knowledge.
Outlook on Microalgal Biofuels Wijffels, René H; Barbosa, Maria J
Science (American Association for the Advancement of Science),
08/2010, Letnik:
329, Številka:
5993
Journal Article
Recenzirano
Microalgae are considered one of the most promising feedstocks for biofuels. The productivity of these photosynthetic microorganisms in converting carbon dioxide into carbon-rich lipids, only a step ...or two away from biodiesel, greatly exceeds that of agricultural oleaginous crops, without competing for arable land. Worldwide, research and demonstration programs are being carried out to develop the technology needed to expand algal lipid production from a craft to a major industrial process. Although microalgae are not yet produced at large scale for bulk applications, recent advances--particularly in the methods of systems biology, genetic engineering, and biorefining--present opportunities to develop this process in a sustainable and economical way within the next 10 to 15 years.
Fermented foods, with a history as long as the human civilization, form an indispensable constituent in our daily life. However, most fermented foods are produced by spontaneous fermentation, and the ...fermentation processes are still uncontrolled. To ensure consistent food quality, it is of paramount importance to understand and control the spontaneous food fermentations.
In spontaneous food fermentations, metabolic activity of a succession of complex microbiota results in desired flavour that is the key criterion to decide consumers’ preference. Therefore, flavour compound formation by microbial metabolism can be used as the control target in spontaneous food fermentations. However, relatively little is known about the complexity of the microbiota associated with the flavour compound formation. Therefore, in this review by using Chinese liquor as a model system, we present key biotechnological aspects of the microbiota crucial for flavour of fermented foods, including the driving forces for the microbiota succession, flavour compound formation, and the regulation of flavour compound formation.
Core microbiota, associated with flavour compound formation, can be identified and eventually used to construct a synthetic (i.e. designed) microbiota. Meanwhile, key environmental factors, affecting the core microbiota, can also be identified and controlled to regulate the synthetic microbiota. Furthermore, modelling can be used to predict, optimize and control the flavour compound formation by the synthetic microbiota, so that such spontaneous food fermentations can become controllable, with the ultimate goal to monitor, control, and improve the quality, productivity and safety of fermented foods.
•Flavour compound can be controlled via regulating microbiota in food fermentation.•Core microbiota and key environmental factors should be identified in fermentation.•Synthetic microbiota can provide a tractable and controllable fermentation.•Environmental parameters are yet another factor to affect the microbiota.•Modelling can be used to predict and optimize the flavour compound formation.
Microalgae based production of single-cell protein Janssen, Marcel; Wijffels, Rene H; Barbosa, Maria J
Current opinion in biotechnology,
June 2022, 2022-Jun, 2022-06-00, 20220601, Letnik:
75
Journal Article
Recenzirano
Odprti dostop
Display omitted
•Microalgal protein content is high and surpasses 50% for production strains.•Microalgal amino acid composition matches well with food and feed requirements.•Current microalgae SCP ...production potential is 22–44 tons protein per hectare per year.•Production cost will decrease upon scale-up, process optimization, and strain improvement.•Direct air capture of CO2, or mixotrophic cultivation on sugars, is required in post-fossil era.
Microalgae express high protein levels and can be produced in contained cultivation systems with low water requirements and complete fertilizer use. The production potential is 22–44 tons of protein per hectare per year although the current production scale is small. Techno economic analyses have shown good potential for scale-up and cost reduction. Large-scale production of microalgae in the post-fossil era will rely on the capture of carbon dioxide from the air, or sugars from crops. Microalgal amino acid composition matches well with requirements for food and feed, which, in combination with novel biomass pre-treatment steps, will guarantee high-quality microalgal protein. For a broadening of the microalgae species available as single-cell protein, novel food approval is required.
Display omitted
•Bead milling + enzymatic hydrolysis efficiently disrupts Chlorella vulgaris.•Bead milling prior to enzymatic hydrolysis improves lipid fractionation.•Bead milling + lipase gives the ...best lipid, protein and carbohydrate recovery.
A combined bead milling and enzymatic hydrolysis process was developed for fractionation of the major valuable biomass components, i.e., proteins, carbohydrates, and lipids from the microalgae Chlorella vulgaris. The cells were treated by bead milling followed by hydrolysis with different hydrolytic enzymes, including lipase, phospholipase, protease, and cellulase. Without enzymatic hydrolysis, the recovery yield of lipids, carbohydrates, and proteins for bead milled biomass was 75%, 31%, and 40%, respectively, while by applying enzymatic treatments these results were improved significantly. The maximum recovery yield for all components was obtained after enzymatic hydrolysis of bead milled biomass by lipase at 37 °C and pH 7.4 for 24 h, yielding 88% lipids in the solid phase while 74% carbohydrate and 68% protein were separated in the liquid phase. The recovery yield of components after enzymatic hydrolysis of biomass without bead milling was 44% lower than that of the milled biomass.
The high-energy input for harvesting biomass makes current commercial microalgal biodiesel production economically unfeasible. A novel harvesting method is presented as a cost and energy efficient ...alternative: the bio-flocculation by using one flocculating microalga to concentrate the non-flocculating microalga of interest. Three flocculating microalgae, tested for harvesting of microalgae from different habitats, improved the sedimentation rate of the accompanying microalga and increased the recovery of biomass. The advantages of this method are that no addition of chemical flocculants is required and that similar cultivation conditions can be used for the flocculating microalgae as for the microalgae of interest that accumulate lipids. This method is as easy and effective as chemical flocculation which is applied at industrial scale, however in contrast it is sustainable and cost-effective as no costs are involved for pre-treatment of the biomass for oil extraction and for pre-treatment of the medium before it can be re-used.
Microalgae productivity was doubled by designing an innovative mixotrophic cultivation strategy that does not require gas–liquid transfer of oxygen or carbon dioxide. Chlorella sorokiniana SAG 211/8K ...was cultivated under continuous operation in a 2 L stirred-tank photobioreactor redesigned so that respiratory oxygen consumption was controlled by tuning the acetic acid supply. In this mixotrophic setup, the reactor was first operated with aeration and no net oxygen production was measured at a fixed acetic acid supply rate. Then, the aeration was stopped and the acetic acid supply rate was automatically regulated to maintain a constant dissolved oxygen level using process control software. Respiratory oxygen consumption was balanced by phototrophic oxygen production, and the reactor was operated without any gas–liquid exchange. The carbon dioxide required for photosynthesis was completely provided by the aerobic conversion of acetic acid. Under this condition, the biomass/substrate yield was 0.94 C-mol x ·C-molS –1. Under chemostat conditions, both reactor productivity and algal biomass concentration were doubled in comparison to a photoautotrophic reference culture. Mixotrophic cultivation did not affect the photosystem II maximum quantum yield (Fv/Fm) and the average-dry-weight-specific optical cross section of the microalgal cells. Only light absorption by chlorophylls over carotenoids decreased by 9% in the mixotrophic culture in comparison to the photoautotrophic reference. Our results demonstrate that photoautotrophic and chemoorganotrophic metabolism operate concurrently and that the overall yield is the sum of the two metabolic modes. At the expense of supplying an organic carbon source, photobioreactor productivity can be doubled while avoiding energy intensive aeration.
PDF
