361 research outputs found
Immobilization of two endoglucanases from different sources
Cellulases are a important family of
hydrolytic enzymes which catalyze the bond of cellulose
and other related cello-oligosaccharide derivates.
Industrial applications require enzymes highly stable and
economically viable in terms of reusability. These costs
can be reduced by immobilizing the cellulases, offering a
potential solution through enzyme recycling and easy
recovery. The covalent immobilization of enzymes is
reported here: one is commercial cellulase from
Aspergillus niger and other one is recombinant enzyme,
named CelStrep it because was isolated from a new
cellulolytic strain, Streptomyces sp. G12,. The optimal pH
for binding is 4.6 for both cellulases and the optimal
enzyme concentrations are 1 mg/mL and 5 mg/mL
respectively. The support for immobilization is a
poliacrylic matrix. Experiments carried out in this work
show positive results of enzyme immobilization in terms
of efficiency and stability and confirm the economic and
biotechnical advantages of enzyme immobilization for a
wide range of industrial applications
Tailoring the specificity of the type C feruloyl esterase FoFaeC from Fusarium oxysporum towards methyl sinapate by rational redesign based on small molecule docking simulations
The type C feruloyl esterase FoFaeC from Fusarium oxysporum is a newly discovered enzyme with high potential for use in the hydrolysis of lignocellulosic biomass but it shows low activity towards sinapates. In this work, small molecule docking simulations were employed in order to identify important residues for the binding of the four model methyl esters of hydroxycinnamic acids, methyl ferulate/caffeate/sinapate/p-coumarate, to the predicted structure of FoFaeC. Subsequently rational redesign was applied to the enzyme’ active site in order to improve its specificity towards methyl sinapate. A double mutation (F230H/T202V) was considered to provide hydrophobic environment for stabilization of the methoxy substitution on sinapate and a larger binding pocket. Five mutant clones and the wild type were produced in Pichia pastoris and biochemically characterized. All clones showed improved activity, substrate affinity, catalytic efficiency and turnover rate compared to the wild type against methyl sinapate, with clone P13 showing a 5-fold improvement in catalytic efficiency. Although the affinity of all mutant clones was improved against the four model substrates, the catalytic efficiency and turnover rate decreased for the substrates containing a hydroxyl substitution
Improved production of succinic acid from Basfia succiniciproducens growing on A-donax and process evaluation through material flow analysis
BackgroundDue to its wide range of applications in the food, pharmaceutical and chemical fields, microbial synthesis of succinic acid is receiving growing attention, generating already relevant industrial results, as well as fueling constant research for improvements. In order to develop a sustainable process, a special focus is now set on the exploitation and conversion of lignocellulosic biomasses into platform chemicals.ResultsIn the present work we used Basfia succiniciproducens BPP7 in separated hydrolysis and fermentation experiments with Arundo donax as starting material. Fed-batch strategies showed a maximal production of about 37g/L of succinic acid after 43h of growth and a productivity of 0.9g/Lh on the pilot scale. Global mass balance calculations demonstrated a hydrolysis and fermentation efficiency of about 75%. Moreover, the application of a material flow analysis showed the obtainment of 88.5 and 52 % of succinic acid, per kg of virgin biomass and on the total generated output, respectively.ConclusionsThe use of fed-batch strategies for the growth of B. succiniciproducens on A. donax improved the titer and productivity of succinic acid on pre-pilot scale. Process evaluation through material flow analysis showed successful results and predicted a yield of succinic acid of about 30% in a fed-batch process that uses A. donax as only carbon source also in the feed. Preliminary considerations on the possibility to achieve an energetic valorization of the residual solid coming from the fermentation process were also carried out
Screening of fungal strains for cellulolytic and xylanolytic activities production and evaluation of brewers’ spent grain as substrate for enzyme production by selected fungi
Brewer’s spent grain (BSG), the solid residue of beer production, is attracting significant
attention as raw material for the production of added value substances, since until recently it was
mainly used as animal feed or deposited in landfills, causing serious environmental problems.
Therefore, this work aimed at developing a bioprocess using BSG as a substrate for the production of
cellulases and xylanases for waste saccharification and bioenergy production. Different fungi were
analyzed for their cellulolytic and xylanolytic abilities, through a first screening on solid media by
assessment of fungal growth and enzyme production on agar containing carboxylmethylcellulose or
xylan as the sole carbon source, respectively. The best cellulase and xylanase producers were subjected
to quantitative evaluation of enzyme production in liquid cultures. Aspergillus niger LPB-334 was
selected for its ability to produce cellulase and xylanase at high levels and it was cultivated on BSG
by solid state fermentation. The cellulase production reached a maximum of 118.04 8.4 U/g of dry
substrate after 10 days of fermentation, while a maximum xylanase production of 1315.15 37.5 U/g
of dry substrate was reached after 4 days. Preliminary characterization of cellulase and xylanase
activities and identification of the enzymes responsible were carried out
Lack of uniqueness for weak solutions of the incompressible porous media equation
In this work we consider weak solutions of the incompressible 2-D porous
media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove
non-uniqueness for solutions in in space and time.Comment: 23 pages, 2 fugure
Optimal lower exponent for the higher gradient integrability of solutions to two-phase elliptic equations in two dimensions
We study the higher gradient integrability of distributional solutions u to the equation div(σ∇u) = 0 in dimension two, in the case when the essential range of σ consists of only two elliptic matrices, i.e., σ ∈ {σ1,σ2} a.e. in Ω. In [9], for every pair of elliptic matrices σ1 and σ2 exponents pσ1,σ2 ∈ (2,+∞) and qσ1,σ2 ∈ (1,2) have been found so that if u ∈ W1,qσ1,σ2(Ω) is solution to the elliptic equation then ∇u ∈ Lpσ1,σ2(Ω) and the optimality of the upper exponent pσ1,σ2 has been proved. In this paper we complement the above result by proving the optimality of the lower exponent qσ1,σ2. Precisely, we show that for every arbitrarily small δ, one can find a particular microgeometry, i.e. an arrangement of the sets σ-1(σ1) and σ-1(σ2), for which there exists a solution u to the corresponding elliptic equation such that ∇u ∈ Lqσ1,σ2-δ, but ∇u Ɇ Lqσ1,σ2-δ. The existence of such optimal microgeometries is achieved by convex integration methods, adapting to the present setting the geometric constructions provided in [2] for the isotropic case
Bioconversion of potato-processing wastes into an industrially-important chemical lactic acid
Lactic acid (LA) is an important biomolecule applied in food, pharmaceutical and chemical areas, mainly to
produce biodegradable polymers, such as poly–lactic acid (PLA). In this work, an efficient fermentative process
for LA production was developed using potato processing waste (PPW) hydrolysate with Lactobacillus pentosus.
After optimization and kinetics studies, LA production reached 150 g/L with a productivity of 1.6 g/L.h in
Erlenmeyer flasks. LA production was also conducted in STR where 110 g/L were reached with a productivity of
2.4 g/L.h. LA recovery consisted of a clarification step, with powdered activated carbon, with further precipi-
tation at low temperature and acidification of calcium lactate for conversion to LA. The process was effective for
contaminants’ removal and clarification, and LA concentration to 416 g/L. Good perspectives for LA production,
recovery and clarification were observed. Future studies will be carried out for LA purification and polymeri-
zation for PLA synthesis
Effectiveness of Chitosan Films Impregnated With Ciprofloxacin for the Prophylaxis of Osteomyelitis in Open Fractures: An Experimental Study in Rats
Background: The systemic antimicrobial prophylaxis is the standard treatment in the prevention of osteomyelitis after open fractures, with topical application of antimicrobials as an alternative due to their high concentrations at the site of the fracture, low systemic concentrations and fewer side effects.
Objectives: This study aimed to evaluate the effectiveness of prophylaxis of osteomyelitis through experimental model of open fractures with the use of chitosan films, whether or not impregnated with ciprofloxacin.
Materials and Methods: In this experimental study, 24 Holtzman rats were distributed into 4 groups of 6 rats each. The CT (control of treatment) group: an open fracture model treated with systemic antimicrobial; the IC (infection control) group: an open fracture untreated model; the C (chitosan) group: an open fracture model treated using a chitosan film; and the CA (chitosan with antimicrobial) group: an open fracture model treated using a chitosan film impregnated with antimicrobial. After 3 weeks the animals were killed by an overdose of anesthetic, and a fragment osseous was removed for histological and microbiological analysis. The comparisons between the groups considered significant values of P ≤ 0.05.
Results: In cultures of the CT group, there was less bacterial growth compared to the results of the cultures of the IC (P = 0.005), C (P = 0.005) and CA (P = 0.009) groups. The inflammation was lower in the CT group compared to the IC (P = 0.014), C (P = 0.001) and CA (P = 0.007) groups.
Conclusions: In this experimental model of open fracture, the chitosan film pure or impregnated with ciprofloxacin was not effective in the prophylaxis of osteomyelitis
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