Di Caprio, FabrizioPipitone, Luca MariaAltimari, PietroPagnanelli, Francesca...
9页
查看更多>>摘要：Understanding the mechanisms of phenol production by microalgae can contribute to the development of microalgal biorefinery processes with higher economic and environmental sustainability. However, little is known about how phenols are produced and accumulate during microalgal cultivation. In this study, both extracellular and intracellular phenol production by two microalgal strains (Tetradesmus obliquus and Chlorella sp.) were investigated throughout a conventional photoautotrophic batch cultivation. The highest intracellular phenol content (10-25 mg g(-1)) and productivity (12-18 mg L-1 d(-1)) were attained for both strains in the first part of the batch, indicating a positive relation with nutrient availability and biomass productivity. Extracellular phenol production was 2-20 fold lower than intracellular phenols, but reached up to 27 mg L-1 for T. obliquus and 13 mg L-1 for Chlorella sp. The latter finding highlights relevant issues about the management of the exhausted culture medium, due to likely antimicrobial effects.
查看更多>>摘要：In the present study, the ability of the marine bacterium Rhodovulum sulfidophilum DSM-1374 to convert, via photo-fermentative process, certain organic acids such as single carbon source (acetate, lactate, malate and succinate) into polyhydroxyalkanoate accumulations within bacterial cells is evaluated. The main goal of the investigation was poly-3-hydroxybutyrate (P3HB) synthesis by a photo-fermentative process. Of the four carbon sources, only succinate simultaneously produced P3HB and H-2 (268 mg/L and 1085 mL/L respectively). Malate was the least productive source for P3HB; the other carbon sources (acetate and lactate) produced a significant amount of polymer (596 mg P3HB/L for acetate and 716 mg P3HB/L for lactate) when R. sulfidophilum was cultured in batch growth conditions. Cumulative P3HB increased significantly when the bacterium was grown under two steps: nutrient sufficient conditions (step 1) followed by macronutrient deficient conditions (step 2). The highest cumulative P3HB was observed at the end of step 2 (1000 mg/L) when R. sulfidophilum was fed with lactate under phosphorus starvation. When grown over 1200 h, under a semi-continuous regimen, the harvested dry-biomass reached a constant content of P3HB (39.1 +/- 1.6 % of cell dry-weight), in the semi-steady state condition. Since lactate is an abundant byproduct of world industries, it can be used to mitigate the environmental impact in a modern circular bio-economy.
Su, Wen-BinLi, Fei-LongLi, Xue-YongFan, Xiao-Man...
8页
查看更多>>摘要：L-Tagatose, a promising building block in the production of many value-added chemicals, is generally produced by chemical routes with a low yield, which may not meet the increasing demands. Synthesis of L-tagatose by enzymatic oxidation of D-galactitol has not been applied on an industrial scale because of the high cofactor costs and the lack of efficient cofactor regeneration methods. In this work, an efficient and environmentally friendly enzymatic method containing a galactitol dehydrogenase for D-galactitol oxidation and a water-forming NADH oxidase for regeneration of NAD(+) was first designed and used for L-tagatose production. Supplied with only 3 mM NAD(+), subsequent reaction optimization facilitated the efficient transformation of 100 mM of D-galactitol into L-tagatose with a yield of 90.2 % after 12 h (obtained productivity: 7.61 mM.h(-1)). Compared with the current chemical and biocatalytic methods, the strategy developed avoids by-product formation and achieves the highest yield of L-tagatose with low costs. It is expected to become a cleaner and more promising mute for industrial biosynthesis of L-tagatose.
Kwak, Jin MyeongLee, YoungsikShin, Sung WookLee, Jae Seong...
6页
查看更多>>摘要：Site-specific integration via genome editing technologies has been implemented in Chinese hamster ovary (CHO) cells for predictable and efficient cell line development and engineering. Various strategies have been employed to enhance knock-in (KI) efficiency for precise homology-directed repair (HDR)-mediated targeted integration of transgenes in CHO cells. Given the cell cycle-dependent regulation of the DNA damage repair pathway, cell cycle synchronization to the HDR-favored S/G2 phase has been successfully utilized in mammalian cells, but the effect is limited in CHO cells. Here, we describe a cell cycle enrichment method to increase HDR-mediated KI efficiency in CHO cells. Existing G1 cell cycle synchronization methods showed transient cell cycle arrest and did not improve KI efficiency. Rather than cell cycle arrest with a high concentration of chemicals followed by a release step, cells were incubated in the presence of a lower concentration of hydroxyurea (HU) to enrich cells in the S phase. HU selection allowed for robust S phase enrichment of CHO cells by up to 70 % and maintained cell viability. This short-term selection resulted in improved KI efficiency by 1.2-1.5 fold compared with cells in the control condition. Overall, this approach serves as a simple and effective strategy for enhancement of site-specific genome engineering in CHO cells.
Sacchi, RaffaeleMasi, PaoloRusso, Giovanni L.Langellotti, Antonio L....
8页
查看更多>>摘要：Biotechnological production of omega-3 polyunsaturated fatty acids (PUFAs) has become a commercial alternative to fish oil in the past twenty years. Compared to PUFA production by fatty fishes, that from microorganisms has increased due to its promising sustainability and high product safety and to increasing awareness in the expanding vegan market. Although autotrophic production by microalgae seems to be more sustainable in the long term, to date most of the microbial production of omega-3 is carried out under heterotrophic conditions using conventional fermentation technologies. The present review critically analyzes the main reasons for this discrepancy and reports on the recent advances and the most promising approaches for its future development in the context of sustainability and circular economy.
查看更多>>摘要：Microalgae are versatile microorganisms with applications in food, energy and fine chemicals, among others. Modelling the dynamics of microalgae inside a photobioreactor is a convenient and inexpensive way to determine the concentration of cells over time. Numerous models have been developed in the literature, but only a few are able to give relevant biological information. Such information can then be used to further improve the production process. The objective of this work was to develop a model for the determination of microalgal dynamics inside a photobioreactor as a function of the environmental conditions, to retrieve the size-specific growth and division rates as well as the number of daughter cells. The results demonstrate how to evaluate the time needed for microalgae to complete a full life-cycle. Inexpensive laboratory-based procedures and mathematical modelling are combined for the determination of relevant biological parameters.
Gatenholm, PaulToriz, GuillermoTenkanen, MaijaStogios, Peter J....
8页
查看更多>>摘要：The coordinated action of carbohydrate-active enzymes has mainly been evaluated for the purpose of complete saccharification of plant biomass (lignocellulose) to sugars. By contrast, the coordinated action of accessory hemicellulases on xylan debranching and recovery is less well characterized. Here, the activity of two family GH115 alpha-glucuronidases (SdeAgu115A from Saccharophagus degradans, and AxyAgu115A from Amphibacillus xylanus) on spruce arabinoglucuronoxylan (AGX) was evaluated in combination with an alpha-arabinofuranosidase from families GH51 (AniAbf51A, aka E-AFASE from Aspergillus niger) and GH62 (SthAbf62A from Streptomyces thermoviolaceus). The alpha-arabinofuranosidases boosted (methyl)-glucuronic acid release by SdeAgu115A by approximately 50 % and 30 %, respectively. The impact of the alpha-arabinofuranosidases on AxyAgu115A activity was comparatively low, motivating its structural characterization. The crystal structure of AxyAgu115A revealed increased length and flexibility of the active site loop compared to SdeAgu115A. This structural difference could explain the ability of AxyAgu115A to accommodate more highly substituted arabinoglucuronoxylan, and inform enzyme selections for improved AGX recovery and use.
查看更多>>摘要：Polyhydroxyalkanoates (PHAs) are polyesters of significant interest due to their biodegradability and properties similar to petroleum-derived plastics, as well as the fact that they can be produced from renewable sources such as by-product streams. In this study, brewer's spent grain (BSG), the main by-product of the brewing industry, was subjected to a set of physicochemical pretreatments and their effect on the release of reducing sugars (RS) was evaluated. The RS obtained were used as a substrate for further PHA production in Burkholderia cepacia, Bacillus cereus, and Cupriavidus necator in liquid cultures. Although some pretreatments proved efficient in releasing RS (acid-thermal pretreatment up to 42.1 gRS L-1 and 0.77 gRS g(-1) dried BSG), the generation of inhibitors in such scenarios likely affected PHA production compared with the process run without pretreatment (direct enzymatic hydrolysis of BSG). Thus, the maximum PHA accumulation from BSG hydrolysates was found in the reference case with 0.31 +/- 0.02 g PHA per g cell dried weight, corresponding to 1.13 +/- 0.06 g L-1 and a PHA yield of 23 +/- 1 mg g(-1) BSG. It was also found that C. necator presented the highest PHA accumulation of the tested strains followed closely by B. cepacia, reaching their maxima at 48 h. Although BSG has been used as a source for other bioproducts, these results show the potential of this by-product as a no-cost raw material for producing PHAs in a waste valorization and circular economy scheme.
查看更多>>摘要：The use of retaining glycoside hydrolases as synthetic tools for glycochemistry is highly topical and the focus of considerable research. However, due to the incomplete identification of the molecular determinants of the transglycosylation/hydrolysis partition (T/H), rational engineering of retaining glycoside hydmlases to create transglycosylases remains challenging. Therefore, to understand better the factors that underpin transglycosylation in a GH51 retaining alpha-L-arabinofuranosidase from Thermobacillus xylanilyticus, the investigation of this enzyme's active site was pursued. Specifically, the properties of two mutants, F26L and L352M, located in the vicinity of the active site are described, using kinetic and 3D structural analyses and molecular dynamics simulations. The results reveal that the presence of L352M in the context of a triple mutant (also containing R69H and N216W) generates changes both in the donor and acceptor subsites, the latter being the result of a domino-like effect. Overall, the mutant R69H-N216W-L352M displays excellent transglycosylation activity (70 % yield, 78 % transfer rate and reduced secondary hydrolysis of the product). In the course of this study, the central role played by the conserved R69 residue was also reaffirmed. The mutation R69H affects both the catalytic nucleophile and the acid/base, including their flexibility, and has a determinant effect on the T/H partition. Finally, the results reveal that increased loop flexibility in the acceptor subsites creates new interactions with the acceptor, in particular with a hydrophobic binding platform composed of N216W, W248 and W302.
NSTL
Elsevier