Evaluation of the Growth Performance of Microalgae Based on Fine pH Changes
Austin Journal of Biotechnology & Bioengineering, 2021
Microalgae are photosynthetic microorganisms with many potential applications in the food, cosmet... more Microalgae are photosynthetic microorganisms with many potential applications in the food, cosmetics, pharmaceutical and environmental industries. Currently, commercial microalgae production remains limited. Therefore, improving the growth and the culture density of the microalgae cultivation is one of the key enablers to open the way to mass production and commercialisation of these microorganisms. The effect of culture pH on the photoautotrophic growth of C. vulgaris over a large range of values has been investigated in pH-regulated cultures. For each microalgae culture, the specific growth rate, the cell density, the chlorophyll content, the intracellular carbon content and the nitrogen source consumption were monitored. Optimal growth and carbon incorporation have been observed at pH of 7.0. The fastest growth rate and highest biomass production of C. vulgaris were 0.074 h-1 and 0.896 g/L respectively. Under these conditions, a maximum carbon content of cells was 49 % (w/w).
Control of the molecular weight of bacterial poly(3-hydroxybutyrate)
SIGLEAvailable from British Library Document Supply Centre- DSC:DXN002380 / BLDSC - British Libra... more SIGLEAvailable from British Library Document Supply Centre- DSC:DXN002380 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Microalgae are photosynthetic microorganisms that have increasingly attracted interest in the las... more Microalgae are photosynthetic microorganisms that have increasingly attracted interest in the last decade due to their potential for industrial applications. One crucial aspect for the industrial-scale valorisation of algae biomass concerns the quality control during its preservation before being treated to obtain the end-product. Monitoring biomass quality is essential and can be potentially accomplished with the aid of specific biochemical indicators called biomarkers. In this context, the main aim of this work was to identify potential indicators of microalgae biomass viability that could be used as markers of its quality during storage/preservation for commercial operations. The health status of a suspension of Chlamydomonas nivalis was assessed at 4 ºC and 25 ºC during 10 days of storage. The use of the pulse-amplitude-modulation technique, based on chlorophyll fluorescence, was a valuable indicator of the culture viability. The measurement of DNA and of chlorophyll in the supe...
Microalgae are photosynthetic microorganisms that have generated increasing interest in recent ye... more Microalgae are photosynthetic microorganisms that have generated increasing interest in recent years due to their potential applications. Their biological capacity to grow faster than higher plants and their ability to convert solar energy into biomass and other bioactive molecules, has led to the development of various culture systems in order to produce different high-value products with commercial interest. The industrialization of the microalgae cultivation process requires the introduction of standardized quality parameters. In order to obtain bioactive compounds with high added value at a commercial level, it is necessary to sustainably produce biomass at a large scale. Such a process would imply specific stress conditions, such as variation in temperature, light or pH. These environmental conditions would make it more difficult to maintain the viability of the culture and protect the yield and condition of the target molecules. The physiological and biochemical impact of these stress factors on the microalgae biomass can be potentially measured by the presence and activity of various biochemical indicators called biomarkers. This review presents an overview of the main techniques that exist for assessing the "quality" of microalgae cultures through quantification of cell viability and vitality by monitoring specific markers indicative of the status of the culture.
Chlorella vulgaris heterotrophic colony development and interaction
Algal Research, 2020
Abstract This study is a first outcome of a series of works on immobilized cultures of Chlorella ... more Abstract This study is a first outcome of a series of works on immobilized cultures of Chlorella vulgaris. Colonies were grown independently on solid media under heterotrophic conditions and their growth was followed by continuous three-dimensional microscopy and image analysis. The growth was assessed by 3D imaging using a structured light microscope and subsequent image processing. Based on the expressions proposed for the height and radius growth dynamics, we concluded that the colonies expanded at a constant rate in the horizontal direction and a decreasing rate in the vertical direction. A spherical cap best describes the shape of the colonies during the growth period. During development, the packing density of the cells in the colony was calculated to occupy 25–40% of the available space. The cell yield was initially much lower than published values and approached those values at the end, indicating that the glucose consumption was dependent on not only the growth and division of cells but also on the activity of old cells. Finally, no colony-colony intraspecies interaction was observed when two colonies were grown in proximity.
The Role of Small Wort Peptides in Brewing Fermentations
Journal of the Institute of Brewing, 2009
ABSTRACT J. Inst. Brew. 115(2), 134–139, 2009 The utilisation of small peptides by brewing yeast ... more ABSTRACT J. Inst. Brew. 115(2), 134–139, 2009 The utilisation of small peptides by brewing yeast is poorly understood despite a wealth of information on peptide transport by other microorganisms. A novel method for detection, isola-tion and measurement of small peptides during brewery wort fermentations was used to monitor utilisation by ale and lager yeast strains. Oligopeptide levels in wort were found to fluctuate throughout the fermentations. Measurement of extracellular protease activity provided evidence that yeast are able to continually regulate protease production in order to break down wort polypeptides into utilisable nitrogeneous materials.
The present study describes a novel yeast model for the prediction of yeast fermentation. The pro... more The present study describes a novel yeast model for the prediction of yeast fermentation. The proposed model considers the possible metabolic pathways of yeast. For each pathway, the time evolution of components, energy (ATP/ADP), and electron carriers (NAD + /NADH) are expressed with limitation factors for all quantities consumed by each respective pathway. In this manner, the model can predict partition of these pathways based on the growth conditions and their evolution over time. Several biological pathways and their stoichiometric coefficients are well-known from literature. It is important to note that most of kinetics parameters have no effect since actual kinetics are controlled by balance of limiting factors. The few remaining parameters were adjusted and compared with the literature when the dataset was available. The model fits our experimental data from yeast fermentation on glucose in non-aerated batch system. The predictive ability of the model and its capacity to represent the intensity of each pathway over time facilitate an improved understanding of interactions between the pathways. The key role of energy (ATP) and electron carrier (NAD +) to trigger the different metabolic pathways during yeast growth is highlighted, while involvement of mitochondrial respiration not being associated with the TCA cycle is also shown.
Preconditioning of yeast with zinc during acid washing was a way of overcoming zinc deficiency in... more Preconditioning of yeast with zinc during acid washing was a way of overcoming zinc deficiency in wort provided that the barm beer was not separated prior to pitch. This is because uptake of zinc by the yeast was not efficient during the acid washing process. The optimum point of zinc supplementation was directly to wort at the exact time of pitching. Zinc addition to hot wort can result in a decrease in the bioavailable zinc concentration in wort and poor fermentation.
Description of the subject. Extracellular enzymes from filamentous fungi are increasingly used in... more Description of the subject. Extracellular enzymes from filamentous fungi are increasingly used in eco-friendly biotransformation processes. Their relevant technological role and their stability towards extreme process conditions make of them the first sustainable solution for the elaboration of bio-based products from biomass conversion. Objectives. This paper describes the isolation of filamentous fungi from decaying plant material in the region of Meknes (northern central Morocco) and the assessment of their ability to breakdown lignocellulose. The objective is to select performant fungi with enzymatic machinery adapted to local environment and with potential for the breakdown of the regional specific lignocellulosic by-products into potentially high-value molecules. Method. Cereals, decaying wood, olive-pomace and -pulp and their composts were used to isolate lignocellulolytic fungi. One hundred twenty-seven pure strains were isolated and screened at 25 °C on selective media with...
Meknes region is a Moroccan olive-processing area generating high amounts of non-valorized Olive ... more Meknes region is a Moroccan olive-processing area generating high amounts of non-valorized Olive Mill Waste (OMW). Fungi are natural decomposers producing varied enzyme classes and effectively contributing to the carbon cycle. However, structural complexity of biomass and modest performances of wild fungi are major limits for local biorefineries. The objective of current research is to assess the ability of local fungi for bioethanol production from OMW using Consolidated Bioprocessing (CBP). This is done by characterizing lignocellulolytic potential of six wood-decay and compost-inhabiting ascomycetes and selecting potent fermentation biocatalysts. High and diversified activities were expressed by Fusarium solani and Fusarium oxysporum: 9.36 IU. mL À1 and 2.88 IU. mL À1 total cellulase activity, 0.54 IU. mL À1 and 0.57 IU. mL À1 laccase activity, respectively, and 8.43 IU. mL À1 lignin peroxidase activity for the latter. F. oxysporum had maximum bioethanol production and yield of 2.47 g.L-1 and 0.84 g.g À1 , respectively, qualifying it as an important bio-agent for single-pot local biorefinery.
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