The Absence of Phasins PhbP2 and PhbP3 in Determines the Growth and Poly-3-hydroxybutyrate Synthesis.

Phasins are proteins located on the surface of poly-3-hydroxybutyrate (P3HB) granules that affect the metabolism of the polymer, the size and number of the granules, and some also have stress-protecting and growth-promoting effects. This study evaluated the effect of inactivating two new phasins (PhbP2 or PhbP3) on the cellular growth, production, and molecular mass of P3HB in cultures under low or high oxygen transfer rates (OTR). The results revealed that under high OTRₘₐₓ conditions (between 8.

Response of Bacillus velezensis 83 to interaction with Colletotrichum gloeosporioides resembles a Greek phalanx-style formation: A stress resistant phenotype with antibiosis capacity.

Plant growth-promoting rhizobacteria, such as Bacillus spp., establish beneficial associations with plants and may inhibit the growth of phytopathogenic fungi. However, these bacteria are subject to multiple biotic stimuli from their competitors, causing stress and modifying their development.

Yeast extracts from different manufacturers and supplementation of amino acids and micro elements reveal a remarkable impact on alginate production by A. vinelandii ATCC9046.

Background: In research and production, reproducibility is a key factor, to meet high quality and safety standards and maintain productivity. For microbial fermentations, complex substrates and media components are often used. The complex media components can vary in composition, depending on the lot and manufacturing process.

83 increases productivity and quality of tomato ( L.): Pre and postharvest assessment.

spp. are well known plant growth promoting bacteria (PGPB) and biological control agents (BCA) due to their capacity to synthesize a wide variety of phytostimulant and antimicrobial compounds. 83 is a strain marketed in Mexico as a foliar biofungicide (Fungifree AB™) which has been used for biological control of five different genera of phytopathogenic fungi () in crops of agricultural importance such as mango, avocado, papaya, citrus, tomato, strawberry, blueberry, blackberry and cucurbits, among others.

Bacillus velezensis 83 a bacterial strain from mango phyllosphere, useful for biological control and plant growth promotion.

Bacillus velezensis 83 was isolated from mango tree phyllosphere of orchards located in El Rosario, Sinaloa, México. The assessment of this strain as BCA (biological control agent), as well as PGPB (plant growth-promoting bacteria), were demonstrated through in vivo and in vitro assays. In vivo assays showed that B.

Improving glucose and xylose assimilation in Azotobacter vinelandii by adaptive laboratory evolution.

Azotobacter vinelandii is a microorganism with biotechnological potential because its ability to produce alginate and polyhydroxybutyrate. Large-scale biotechnological processes are oriented to sustainable production by using biomass hydrolysates that are mainly composed by glucose and xylose. In the present study, it was observed that A.

Molecular weight and viscosifying power of alginates produced by mutant strains of under microaerophilic conditions.

Alginates are polysaccharides that are of interest in various industrial applications. This is due to the viscosifying properties of alginates, which depends on the weight-average molecular weight. The aim of the present study was to evaluate the changes in alginate quality, in terms of the viscosifying power and weight-average molecular weight of the polymer produced by mutant strains in shake flasks under microaerophilic conditions.

Glucose limitation and glucose uptake rate determines metabolite production and sporulation in high cell density continuous cultures of Bacillus amyloliquefaciens 83.

Bacillus amyloliquefaciens spores have been used as the principal ingredient of biocontrol products. However, during the process of spore production, wild-type strains produce poly-γ-glutamic acid (γ-PGA), an undesirable byproduct that increases broth viscosity and hinders recovery and drying. This work examined the influence of specific glucose uptake rates (q) in glucose-controlled overflow metabolism.

Analysis of respiratory activity and carbon usage of a mutant of Azotobacter vinelandii impaired in poly-β-hydroxybutyrate synthesis.

In this study, the respiratory activity and carbon usage of the mutant strain of A. vinelandii AT6, impaired in poly-β-hydroxybutyrate (PHB) production, and their relationship with the synthesis of alginate were evaluated. The alginate yield and the specific oxygen uptake rate were higher (2.

Diffusional and transcriptional mechanisms involved in laccases production by Pleurotus ostreatus CP50.

The independent effects of hydrodynamic stress (assessed as the Energy Dissipation/Circulation Function, EDCF) and dissolved oxygen tension (DOT) on the growth, morphology and laccase production by Pleurotus ostreatus CP50 were studied using a 3(2) factorial design in a 10L reactor. A bell-shape function for fungus growth between 8 and 22% DOT was observed, as well as a significant negative effect on laccase production and the expression of poxc, the gene encoding for the most abundant laccase produced by P. ostreatus CP50.

Toward an understanding of the effects of agitation and aeration on growth and laccases production by Pleurotus ostreatus.

Mycelial growth and laccase production by Pleurotus ostreatus CP50 cultured in a 10-L mechanically agitated bioreactor were assessed through a 2(3) factorial experimental design. The main effects and interactions of three factors (agitation, aeration and copper induction) over five responses (μ, αLacc, βLacc, maximal volumetric laccase activity and maximal biomass concentration) were analyzed. P.

Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii.

The transcription of genes involved in alginate polymerization and depolymerization, as well as the alginase activity (extracellular and intracellular) under oxygen-limited and non oxygen-limited conditions in cultures of A. vinelandii, was studied. Two levels of dissolved oxygen tension (DOT) (1% and 5%, oxygen-limited and non-oxygen-limited, respectively) strictly controlled by gas blending, were evaluated in a wild type strain.

The acetylation degree of alginates in Azotobacter vinelandii ATCC9046 is determined by dissolved oxygen and specific growth rate: studies in glucose-limited chemostat cultivations.

Alginates are polysaccharides that may be used as viscosifiers and gel or film-forming agents with a great diversity of applications. The alginates produced by bacteria such as Azotobacter vinelandii are acetylated. The presence of acetyl groups in this type of alginate increases its solubility, viscosity, and swelling capability.

Azotobacter vinelandii lacking the Na(+)-NQR activity: a potential source for producing alginates with improved properties and at high yield.

The mutant ATCN4 strain of Azotobacter vinelandii, which lacks the Na(+)-NQR activity and results in an alginate overproduction (highly mucoid phenotype), was cultured in shake flasks in minimal and rich medium, and the chemical composition and rheological properties of the alginate were determined. Mutant ATCN4 exhibited a high efficiency for sucrose conversion to alginate and PHB accumulation, reaching yields that were 3.6- and 1.

Oxygen transfer rate during the production of alginate by Azotobacter vinelandii under oxygen-limited and non oxygen-limited conditions.

Background: The oxygen transfer rate (OTR) and dissolved oxygen tension (DOT) play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum oxygen transfer rate (OTRmax) in cultures where the dissolved oxygen tension (DOT) was kept constant.

Increasing Pleurotus ostreatus laccase production by culture medium optimization and copper/lignin synergistic induction.

Laccases have great biotechnological potential in diverse industries as they catalyze the oxidation of a broad variety of chemical compounds. Production of laccases by basidiomycetes has been broadly studied as they secrete the enzymes, grow on cheap substrates, and they generally produce more than one isoenzyme (constitutive and/or inducible). Laccase production and isoenzyme profile can be modified through medium composition and the use of inducers.

The influence of circulation frequency on fungal morphology: a case study considering Kolmogorov microscale in constant specific energy dissipation rate cultures of Trichoderma harzianum.

The energy dissipation/circulation function (EDCF) is the product of the specific energy dissipation rate in the impeller swept volume (P/kD(3)) and the frequency of particle circulation (1/t(c)) through that volume. A direct relationship between mycelial fragmentation and EDCF has been reported. However, and although hyphal fragmentation is assumed to occur by hyphae-eddy interaction, Kolmogorov microscale (lambda) has not been shown to determine, at least directly, fungal morphology.

Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii.

Several aspects of alginate and PHB synthesis in Azotobacter vinelandii at a molecular level have been elucidated in articles published during the last ten years. It is now clear that alginate and PHB synthesis are under a very complex genetic control. Genetic modification of A.

Living with heterogeneities in bioreactors: understanding the effects of environmental gradients on cells.

The presence of spatial gradients in fundamental culture parameters, such as dissolved gases, pH, concentration of substrates, and shear rate, among others, is an important problem that frequently occurs in large-scale bioreactors. This problem is caused by a deficient mixing that results from limitations inherent to traditional scale-up methods and practical constraints during large-scale bioreactor design and operation. When cultured in a heterogeneous environment, cells are continuously exposed to fluctuating conditions as they travel through the various zones of a bioreactor.

6-pentyl-alpha-pyrone production by Trichoderma harzianum: the influence of energy dissipation rate and its implications on fungal physiology.

The influence of the agitation conditions on biomass growth, morphology, carbon metabolism, viability, and 6-pentyl-alpha-pyrone (6PP) production by Trichoderma harzianum were studied in an extractive fermentation system. Batch spore-inoculated cultures developed at dissolved oxygen concentrations above 35% of air saturation were carried out in a 14 L bioreactor. The effect of energy dissipation rate over culture performance was assessed using two sets of three Rushton turbines (having different diameters) operated at different agitation speeds.

Development of advanced image analysis techniques for the in situ characterization of multiphase dispersions occurring in bioreactors.

Fermentation bioprocesses typically involve two liquid phases (i.e. water and organic compounds) and one gas phase (air), together with suspended solids (i.

Rhizoctonia solani, an elicitor of 6-pentyl-alpha-pyrone production by Trichoderma harzianum in a two liquid phases, extractive fermentation system.

6-pentyl-alpha-pyrone (6PP) production by Trichoderma harzianum, in an extractive fermentation system, was elicitated by Rhizoctonia solani. The extent of 6PP elicitation was related to the state of Rhizoctonia and to the Trichoderma inoculum type. The use of non-viable Rhizoctonia solani mycelium in mycelium-inoculated Trichoderma harzianum culture, yielded the maximal 6PP production (474 mg l(-1)) compared to control cultures (147 mg l(-1)) and decreased the process time from 192 to 96 h.

Phases dispersion and oxygen transfer in a simulated fermentation broth containing castor oil and proteins.

The sizes of air bubbles and castor oil drops were studied by image analysis as a function of the concentration of soluble protein (bovine serum albumin [BSA] and lipase, as model proteins) in a three-phase system using a simulated fermentation medium (aqueous salt solution, castor oil, and air). Small amounts of proteins (<0.02 g/L) caused an important decrease in oil drops and bubbles sizes, together with a pronounced decrease in surface tension.

Quantitative characterisation of the morphology of Trichoderma harzianum cultured in shake-flasks and containing tween 40.

Image analysis was used to measure the effect of Tween 40 on the morphology of Trichoderma harzianum. The percentage of pellets was maximal (93%) with Tween at 0.2 ml l(-1), whereas the maximal proportion of dispersed mycelia (40%) was with Tween at 1.