Rate Of Hydrolysis Research Articles

Differences in protein hydrolysis on quality of fermented milk: The changes in structure and processing characteristics

The functions and sensory properties of fermented dairy products are influenced by numerous factors, including the type of milk, the strain's degree of protein hydrolysis, and the additives of fermented milk. Currently, a large number of studies have demonstrated that the proteolytic ability of probiotics significantly affects the gel properties of fermented milk. However, few studies have examined the effects of probiotics with varying proteolytic abilities on the functions and sensory properties of fermented dairy products from the protein conformation perspective. Therefore, this study screened Lactobacillus helveticus KLDS1.8701 with a high protein hydrolysis rate and Lactobacillus helveticus KLDS1.0633 with a low hydrolysis rate to investigate the effects of varying degrees of protein hydrolysis on the gel properties, sensory properties and protein conformation of fermented milk. The results showed that the fermented milk containing Lactobacillus helveticus KLDS1.0633 with a low protein hydrolysis degree had high WHC, hardness and viscosity, a dense and uniform structure, abundant pores, and good texture and sensory properties. In addition, compared with fermented milk with high protein hydrolysis, low protein hydrolysis also increased the content of disulfide bonds, low surface hydrophobicity, and more hydrophilic structures such as a-helix. This study explains the impact of differences in protein hydrolysis degree among strains on fermented milk from a new perspective of protein secondary and tertiary conformations, which provides new insights for selecting suitable strains to produce fermented milk with better taste and nutrition.

Allosteric mechanism of synergistic effect in α- and β-amylase mixtures

Alpha-amylase and beta-amylase coexist as mixtures in industrial production, and the two amylases have active synergistic effects when they approach each other. These effects are due to enhanced enzyme binding affinity for the substrate and the rate of particle hydrolysis. Here, we report the allosteric mechanism of this synergistic effect in α- and β-amylase mixtures. The assay showed higher activity after mixing α- and β-amylase. Molecular docking showed that α- and β-amylase create a stable dual-enzyme complex with high binding energy, and that complex formation does not affect the exposure of respective active sites. β-Amylase is specifically bound to the B domain of α-amylase, and the dynamic plasticity of the B domain makes it move spatially, and this adjustment leads to a more open conformation in the active site of α-amylase. Because the enzymes binding make the complex more stable, the degree to which the relative activity of the dual-enzyme complex is inhibited is significantly reduced. After enzyme hydrolysis, the products maltose and glucose accumulate and produce competitive inhibition, which explains the relative activity decrease of the later-stage dual-enzyme cooperation. Structural characterization by FT-IR and CD spectroscopy did not reveal significant changes in respective secondary structures after enzyme binding.

Efficient Biosynthesis of Theanderose, a Potent Prebiotic, Using Amylosucrase from Deinococcus deserti.

The study aimed to develop an efficient bioprocess for the discovery and synthesis of theanderose by using amylosucrase from Deinococcus deserti (DdAS). An unknown trisaccharide produced by DdAS was detected by high-performance anion-exchange chromatography-pulsed amperometric detection and high-performance liquid chromatography-evaporative light scattering detection, purified using medium-pressure liquid chromatography, and identified as theanderose (α-d-glucopyranosyl-(1→6)-α-d-glucopyranosyl-(1→2)-β-d-fructofuranoside) through nuclear magnetic resonance and mass spectrometry. DdAS synthesized theanderose with a 25.4% yield (174.1 g/L) using 2.0 M sucrose at 40 °C for 96 h. In an in vitro digestion model, theanderose showed a 6.5% hydrolysis rate over 16 h. Prebiotic efficacy tests confirmed that theanderose significantly enhanced the proliferation of selected Bifidobacterium strains in the culturing medium with theanderose as the main carbon source. Subsequently, fecal fermentation was performed by adding theanderose to the feces of 20 individuals of varying ages to assess its effect on the gut microbiota. Theanderose increased the relative abundance of Bifidobacteriaceae and Prevotellaceae while decreasing the population ratio of Lachnospiraceae and Ruminococcaceae. Conclusively, theanderose displayed excellent prebiotic potential when judged by low digestibility and selective growth of beneficial microbes over harmful microbes.

Controlled fabrication of hierarchical porous carbon nanospheres with high doped nitrogen content for high-performance adsorbent of biomacromolecule

Constructing nitrogen-doped porous carbons with high specific surface area, rapid mass transfer channels, and positive charge is a crucial requirement for high-performance adsorbents. Herein, by the kinetic self-assembly synthesis strategy, we prepared nitrogen-doped hierarchical porous carbon spheres (N-HPCS) with adjustable pore structure, high specific surface area, and high nitrogen doping content (8.88 %). By using ethylenediamine as an assisted polymerization and assembly agent, the hydrolysis and condensation rate of tetraethyl orthosilicate (TEOS) as the silica source and the condensation rate of 3-aminophenol and formaldehyde as the phenolic resin precursor were controlled by adjusting ammonia volume as the alkaline catalyst to tune kinetic self-assembly of silica and phenolic resin components, thus achieving their simultaneous or sequential nucleus and growth. After carbonization and selective silica etching, three types of carbon nanospheres with center-radial pores, hollow center-radial pores and hollow structure were obtained. High nitrogen doping content endowed the nanospheres with positive charge. Through adsorption experiments on the bovine serum albumin (BSA) and Hemoglobin (Hb) as typical biological macromolecules, hollow carbon nanospheres with center-radial pores exhibited excellent adsorption performance for BSA(622.34 mg g−1) and Hb(759.96 mg g−1). Our fabricated N-HPCS may become a potential candidate for high-performance adsorption materials.

Effects of NaOH and Na2CO3 pretreatment on the saccharification of sweet sorghum bagasse

In this work, the chemical composition, chemical structures, and sugar release were evaluated for sweet sorghum bagasse (SSB) biomass in response to alkaline pretreatments and enzymatic hydrolysis. Five different ratios of 2 M sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) solutions were used for biomass fractionation along with two heat treatment conditions, 85°C and 150°C for 1 h. Sugar yields from enzymatic hydrolysis were measured at different durations up to 72 h. SSB samples pretreated at high temperature using alkaline solutions containing equal amounts of Na2CO3 and NaOH favored retaining cellulose content (up to 90%) while effectively removing hemicellulose (65%) and lignin (92%). The high-temperature pretreatment conditions resulted in improved delignification, higher sugar concentrations, and sugar yields. Pretreatment solutions consisting of 50% or more NaOH produced higher glucose yields (85%–90%) and total sugar concentrations. Moreover, pretreatment solutions containing Na2CO3 improved the hydrolysis rates allowing SSB samples reach maximum yields faster than those without it, 48 versus 72 h. Results showed pretreatment methods combining NaOH and Na2CO3 were effective at promoting SSB biomass conversion, increasing sugar recovery after hydrolysis, and reducing the hydrolysis duration, all of which are desirable and cost beneficial.

Fusion of Hydrophobic Anchor Peptides Promotes the Hydrolytic Activity of PETase but not the Extent of PET Depolymerization

Enzymatic recycling of polyethylene terephthalate (PET) has attracted significant attention in recent years. While the fusion of anchor peptides to PET hydrolases is believed to enhance PET hydrolytic activity, a quantitative analysis is yet lacking. Here, we construct four fusion enzymes by fusing anchor peptides (including hydrophobic LCI, LCIM1 and TA2, and hydrophilic EK4) to the C terminus of HotPETase, one of the most active PET hydrolases for high‐crystallinity PET (HC‐PET). Single‐molecule force spectroscopy (SMFS) demonstrates that hydrophobic anchor peptides promote adhesive interactions between the fusion enzymes and the PET surface. This is also validated by the adsorption kinetics and isotherms, and the saturated adsorption capacity remains unaltered compare to HotPETase. At low substrate loadings, the apparent hydrolytic activity of these fusion enzymes is positively related to the hydrophobicity of the anchor peptides. Among them, HotPETase‐LCI stands out as the most effective enzyme for HC‐PET degradation, demonstrating a 1.5‐fold increase in hydrolytic activity. At high substrate loadings, the advantages of fusion with anchor peptides diminish. We conclude that fusion enzymes only facilitate the hydrolytic rates of HC‐PET but have little effect on the final conversion extent.

Enhanced anaerobic digestion of freezing and thawing pretreated cow manure with increasing solid content: kinetics and microbial community dynamics

High solid anaerobic digestion has proved the mainstream technology for the treatment of organic wastes. However, the high molecular weight and complex lignocellulosic structure of cow manure (CM) make it indigestible and inefficient, leading to limit the hydrolysis step of anaerobic digestion at high solid content. To mitigate this bottleneck, an improved cost-effective freezing and thawing pretreatment technique was proposed in this study. The freezing and thawing pretreatment of raw CM without any dilution was done for 20 days. The maximum cumulative methane yield (487 mL CH4 g− 1VS) was achieved at a total solid (TS) of 5% followed by TS of 10% and 15%, which was 13%, 20% and 21% higher than obtained from untreated CM, respectively. The kinetic results revealed that the biodegradable materials could be utilized at increasing TS with decreasing hydrolysis rate. The pretreatment significantly enhanced the methylotrophic methanogenic pathway during high solid anaerobic digestion, which was contrary to the general concept that the process is usually dominated by acetoclastic and hydrogenotrophic methanogens. This study is very important to understand the effect of solid content but also important to understand the effect of freezing and thawing pretreatment on process parameters and microbial community dynamics in high solid anaerobic digestion.

Low Fibrillation Lyocell Fiber: Analysis of Fiber and its Crosslinking Agent

AbstractIn this paper, the hydrolysis process of Dichlorohydroxytriazine (NHDT) under alkaline conditions are studied. A qualitative and quantitative method for the determination of HNDT and its hydrolysis products are established, which further clarified the hydrolysis mechanism of NHDT. Under alkaline conditions, the hydrolysis products are mainly compound 4, compound 6 and chloride (Cl−). The hydrolysis rate of NHDT at different NaOH concentration and temperature is studied. This research can be used to guide the high efficiency preparation of low fibrillation Lyocell fiber. According to the quantitative detection of wet abrasion numbers and the qualitative analysis of the fiber by SEM after slapping, it is concluded that the low fibrillation Lyocell fiber is less prone to fibrillation under the combined action of wet state and mechanical force. Due to hydrolysis of the unreacted second chlorine resulting in harmful products on the low fibrillation Lyocell fiber, the fibrillation propensity increased with the increase of storage time. The mechanical properties of low fibrillation Lyocell fiber prepared under different fiber states are studied. The tensile breaking strength of low fibrillation Lyocell fiber prepared in the form of sequentially arranged fiber bundles are better, which is closely related to the fiber surface.

Influence of lecithin on the digestibility and immunoreactivity of β-conglycinin

A growing body of evidence suggests that protein structure can be uniquely altered by lipids. However, the role of lecithin on the digestibility and immunoreactivity of allergenic protein remains poorly understood. Therefore, we investigated the impact of different protein/lecithin (P:L) ratios (5:1, 10:1, 20:1, 30:1 and 40:1) on the digestion properties, peptide profiles and immunoreactivity of β-conglycinin in vitro simulated gastrointestinal digestion. Results revealed that lecithin addition increased the degree of hydrolysis and digestion rate of β-conglycinin during digestion in a dose-dependent manner, which may be attributed to the enhancement of pepsin activity. Additionally, the addition of lecithin contributed to the dispersion and homogeneity of β-conglycinin digestion products. When the ratio of lecithin to β-conglycinin was 1:10, the obtained β-conglycinin digestion products exhibited the highest DH value (23.80 %) and the lowest antigenicity (52.69%) in the intestinal digestion. Peptidomics and immunoinformatic analysis further confirmed that PL-10 disrupted 18/30, 15/44, and 37/75 epitopes in the α, α′, and β subunits of β-conglycinin, respectively. These results suggested that lecithin changed the cleavage preferences of β-conglycinin, and promoted the disruption of allergic epitopes, specifically for the β subunit. The study can contribute to our understanding of the role of lecithin in the digestion properties and immunoreactivity of allergenic protein.

Anaerobic digestion of dairy cow and goat manure: Comparative assessment of biodegradability and greenhouse gas mitigation

This study evaluated the anaerobic digestion (AD) of dairy cow and goat manure from dairy farming operations. The physicochemical characteristics, biodegradability and greenhouse gas emissions (GHG) reduction potential were assessed. Dairy goat manure exhibited higher volatile solids (16 % vs. 10 %) and 34 % greater chemical oxygen demand content (COD) compared to cow manure, indicating better suitability for AD. However, biochemical methane potential tests revealed higher methane yields from cow manure (81 % biodegradability) compared to goat manure (26 % biodegradability), attributed to slower hydrolysis rates and recalcitrant composition of goat manure. Both manures displayed suboptimal carbon-to-nitrogen ratios (<20:1) and excessive levels of mineral nutrients such as calcium. The ammonia–nitrogen and volatile fatty acid levels remained below threshold limits throughout the anaerobic digestion process, indicating no significant accumulation or inhibition. Recovering biogas through AD showed potential GHG reductions of 64 % (2.21 t CO2-eq/cow·year) and 69 % (0.27 t CO2-eq/goat·year) compared to conventional manure management practices. While pretreatment and co-digestion could enhance biogas production, further research is needed to optimise these strategies for efficient resource recovery and environmental sustainability in dairy farming operations.Abbreviations: AD, anaerobic digestion; AWMS, animal waste management systems; BMP, biochemical methane potential; CHNS, carbon, hydrogen, nitrogen, and sulphur; C/N, carbon-to-nitrogen, COD, chemical oxygen demand; GC-FID, gas chromatography-flame ionisation detection; GHG, greenhouse gas; GWPM, global warming potential of methane; He, helium; ICP-MS, inductively coupled plasma mass spectrometry; I/S, inoculum-to-substrate ratio; IPCC, International Panel on Climate Change; NH3-N, ammonia–nitrogen; SD, standard deviation; TBMP, theoretical biochemical methane potential; TN, total nitrogen; TS, total solids; VFAs, volatile fatty acids; VS, volatile solids.

ATP-induced reconfiguration of the micro-viscoelasticity of cardiac and skeletal myosin solutions.

We study the high-frequency, micro-mechanical response of suspensions composed of cardiac and skeletal muscle myosin by optical trapping interferometry. We observe that in low ionic strength solutions, upon the addition of magnesium adenosine triphosphate (MgATP2-), myosin suspensions radically change their micro-mechanics properties, generating a viscoelastic fluid characterized by a complex modulus similar to a suspension of worm-like micelles. This transduction of energy, from chemical to mechanical, may be related to the relaxed states of myosin, which regulate muscle contractility and can be involved in the etiology of many myopathies. Within an analogous generic mechanical response, cardiac and skeletal myosin suspensions provide different stress relaxation times, elastic modulus values, and characteristic lengths. These discrepancies probably rely on the dissimilar physiological functions of cardiac and skeletal muscle, on the different MgATPase hydrolysis rates of cardiac and skeletal myosins, and on the observed distinct cooperative behavior of their myosin heads in the super-relaxed state. In vitro studies like these allow us to understand the foundations of muscle cell mechanics on the micro-scale, and may contribute to the engineering of biological materials whose micro-mechanics can be activated by energy regulators.

Supramolecular structure and in vitro digestive properties of plasma-treated corn starches varying in amylose content

The effects of plasma treatment on the multi-scale structure and in vitro digestibility of maize starch with different amylose contents were systematically evaluated. The results demonstrated that all maize starches' molecular weights (MW) decreased when treated with plasma, among which the MW of waxy maize starch displayed the largest reduction. Plasma treatment led to an increase in the thickness of the semi-crystalline lamellae and double helix proportions of waxy and normal maize starches. However, high-amylose maize starch presented a less ordered structure by plasma treatment. Additionally, larger pores and channels were observed on the surface of plasma-treated waxy and normal maize starch granules. Moreover, deposits were displayed on the surface of high-amylose maize starch granules. These changes increased the in vitro digestibility and hydrolysis rate of three starches after plasma treatment. Notably, plasma treatment caused diverse alterations in the structure and functionality of maize starch varying in amylose content, leading to maize starch with better digestibility, therefore being used as an ingredient for functional foods.

Insights on the polymerization kinetics of non-isocyanate polyurethanes (NIPU) using in situ NMR spectroscopy

An in situ characterization method using liquid Nuclear Magnetic Resonance (NMR) spectroscopy has been developed to aid the preparation of highly reactive non-isocyanate polyurethanes (NIPUs) from cyclic carbonate aminolysis. Using this methodology, the aminolysis kinetics and the final polymer structure of a model NIPU obtained by reaction of a 5-membered bis-cyclic carbonate (5CC) and 1,4-diaminobutane have been fully investigated, as a function of the type and concentration of the aminolysis catalyst, and the reaction temperature. Several catalysts already reported in NIPUs syntheses, including 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), have been compared. The kinetics of the 5CC hydrolysis side reaction was also studied. With an activation energy of 29.7 kJ mol−1, TBD was clearly the most efficient catalyst used, allowing 5CC conversion ratio of up to 100 % using a concentration of 0.35 eq5CC. However, under these experiment conditions, TBD concentration also showed to have a non-negligible influence on the hydrolysis rate, representing between 6 and 14 % of the initial 5CC concentrations, at 353 K. Neither the catalyst or the temperature seemed to affect the polymer structure, with secondary hydroxyl-containing isomer proportions of (70 ± 6) %. Finally, this in situ NMR method is paving the way for rapid screening of innovative catalysts for sustainable NIPU synthesis.

Effect of aeration pretreatment on anaerobic digestion of swine manure

ABSTRACT To investigate the effects of aeration pretreatment on the anaerobic digestion (AD) of swine manure, five pretreatment groups were established with dissolved oxygen (DO) in each group set to 0.0, 0.4, 0.8, 1.4, and 2.0 mg/L, respectively. The results demonstrated that compared to the non-aeration group, methane production increased to varying degrees with different aeration pretreatments (AP), with a maximum increase of 27.98% (DO = 2.0 mg/L). AP reduced the hydrogen sulfide (H2S) content of biogas. The H2S concentration in the DO = 2.0 mg/L was only 0.209%, and this represented an increased H2S removal rate of 49.27% compared to that of the DO = 0.0 mg/L (0.412%). Simultaneously, AP increases the hydrolysis rate. When the DO concentration reached 2.0 mg/L, the hydrolysis rate reached its maximum. An increase in the hydrolysis rate further enhanced the removal rate of organic matter. The organic matter removal rate was highest (36.96%) at DO = 2.0 mg/L. AP effectively prolonged the methane generation time and shortened the lag time of methane generation. AP creates a brief micro aerobic environment, accelerates substrate hydrolysis, and promotes the production and consumption of total volatile fatty acids, particularly acetic acid. Additionally, AP promoted the symbiotic relationship between Caldicoprobacter (20.93%–34.96%) and Metanosaeta (14.73%–18.45%).

Mammalian Esterase Activity: Implications for Peptide Prodrugs.

As a traceless, bioreversible modification, the esterification of carboxyl groups in peptides and proteins has the potential to increase their clinical utility. An impediment is the lack of strategies to quantify esterase-catalyzed hydrolysis rates for esters in esterified biologics. We have developed a continuous Förster resonance energy transfer (FRET) assay for esterase activity based on a peptidic substrate and a protease, Glu-C, that cleaves a glutamyl peptide bond only if the glutamyl side chain is a free acid. Using pig liver esterase (PLE) and human carboxylesterases, we validated the assay with substrates containing simple esters (e.g., ethyl) and esters designed to be released by self-immolation upon quinone methide elimination. We found that simple esters were not cleaved by esterases, likely for steric reasons. To account for the relatively low rate of quinone methide elimination, we extended the mathematics of the traditional Michaelis-Menten model to conclude with a first-order intermediate decay step. By exploring two regimes of our substrate → intermediate → product (SIP) model, we evaluated the rate constants for the PLE-catalyzed cleavage of an ester on a glutamyl side chain (kcat/KM = 1.63 × 103 M-1 s-1) and subsequent spontaneous quinone methide elimination to regenerate the unmodified peptide (kI = 0.00325 s-1; t1/2 = 3.55 min). The detection of esterase activity was also feasible in the human intestinal S9 fraction. Our assay and SIP model increase the understanding of the release kinetics of esterified biologics and facilitate the rational design of efficacious peptide prodrugs.

Evaluating the Hydrothermal Stability of Superbase-Based Ionic Liquids in Cellulose Fiber Spinning.

This study highlights the substantially improved hydrothermal stability of 7-methyl-1,5,7-triazabicyclo[4.4.0] dec-5-enium [mTBDH]+ in [mTBDH][MeOCH2COO] compared to [mTBDH][OAc], as well as the strong cellulose dissolution capability of [mTBDH][MeOCH2COO] and excellent spinnability with a maximum draw ratio of 14. These findings demonstrate the high potential of using [mTBDH][MeOCH2COO] as the solvent to advance Ioncell fiber spinning technology by reducing the hydrolysis rate of [mTBDH]+, thereby minimizing loss during solvent recycling processes.

In Silico Design of Novel RGS2-Galpha-q Interaction Inhibitors with Anticancer Activity.

Regulators of G-protein signaling (RGS) are a family of approximately 30 proteins that bind to and deactivate the alpha subunits of G-proteins (Gα) by accelerating their GTP hydrolysis rates, which terminates G-protein coupled receptor (GPCR) signaling. Thus, RGS proteins are essential in regulating GPCR signaling, and most members are implicated as critical nodes in human diseases such as hypertension, depression, and others. Regulator of G-protein signaling 2 (RGS2), a member of the R4 family of RGS proteins, is overexpressed in many solid breast cancers, and its levels in prostate cancer significantly correlate with the metastatic stage and poor prognosis. We sought to develop RGS2 inhibitors as potential chemotherapeutic agents utilizing structure-based drug design approaches. Available structures of the RGS2-Gα complex were used to extract a pharmacophore model for searching chemical databases. Docking of identified hits to RGS2 as well as other RGS structures was used to screen the hits for potent and selective RGS2 inhibitors. Whole cell assays showed the top 10 ranking compounds, AJ-1-AJ-10, to inhibit RGS2-Gαq interactions. Differential scanning fluorimetry showed AJ-3 to bind RGS2 but not Gαq. All 10 compounds inhibited the growth of several RGS2 expressing cancers in cell culture assays. In addition, AJ-3 inhibited the migration of LNCaP prostate cancer cells in wound healing assays. This is the first group of RGS2 inhibitors identified by structure-based approaches and that show anticancer activity. These results highlight the potential RGS2 inhibitors have to be a new class of chemotherapeutic agents.

Uncovering the toxic effects and adaptive mechanisms of aminated polystyrene nanoplastics on microbes in sludge anaerobic digestion system: Insight from extracellular to intracellular

The impacts of polystyrene nanoplastics (PS NPs) with amino functional groups on sludge anaerobic digestion process and the underlying microbial feedbacks remains unclear. Herein, PS NPs coated with and without amino functional groups were employed to explore their impacts on the sludge digestion performance. Experimental results showed that aminated PS NPs (PS-NH2) deteriorated the methane yield and hydrolysis rate. The Derjaguin-Landau-Verwey-Overbeek theory analysis suggested that the PS-NH2 decreased the interaction energy barrier, making it easier to contact with sludge and disrupting the structure of extracellular polymeric substances. Metagenomic analysis showed that the abundance of functional microbes (e.g., Longilinea, Leptolinea, and Methanosarcina) decreased, accompanied with lower network complexity and fewer keystone taxa. Molecular docking revealed that PS-NH2 occupy the antioxidant enzyme active binding sites through hydrogen bonding and hydrophobic interactions, impairing degradation of reactive oxygen species. The severe intracellular oxidative stress up-regulated genes associated with quorum sensing (e.g., luxI and luxR) and protein biosynthesis (e.g., algA, trpG and trpE), and further inducing compact tryptophan-like proteins as a defense against NPs. These findings provide new understanding of the toxic effects from PS-NH2 in biological systems and offer valuable insights into the regulation strategies aimed at alleviating NPs inhibition.

Cryo-EM visualizes multiple steps of dynein's activation pathway.

Cytoplasmic dynein-1 (dynein) is an essential molecular motor controlled in part by autoinhibition. We recently identified a structure of partially autoinhibited dynein bound to Lis1, a key dynein regulator mutated in the neurodevelopmental disease lissencephaly. This structure provides an intermediate state in dynein's activation pathway; however, other structural information is needed to fully explain Lis1 function in dynein activation. Here, we used cryo-EM and samples incubated with ATP for different times to reveal novel conformations that we propose represent intermediate states in the dynein's activation pathway. We solved sixteen high-resolution structures, including seven distinct dynein and dynein-Lis1 structures from the same sample. Our data also support a model in which Lis1 relieves dynein autoinhibition by increasing its basal ATP hydrolysis rate and promoting conformations compatible with complex assembly and motility. Together, this analysis advances our understanding of dynein activation and the contribution of Lis1 to this process.

A Kinetic Study on Chronic Response of Activated Sludge to Diclofenac by Respirometry

The present study investigated the chronic response of activated sludge to the emerging pollutant diclofenac as well as its aerobic biodegradation potential at different sludge retention times (SRTs). The impact of prolonged exposure to diclofenac on microbial process kinetics was explored with respirometric modelling. The long-term operation of lab-scale reactors revealed that continuous feeding of diclofenac at relevant concentrations observed in municipal wastewaters did not affect carbon removal efficiency independentl of SRT. However, in case of diclofenac removal, 34% efficiency could be achieved at a higher SRT of 20 days. Kinetic evaluation showed that the increment in diclofenac dosing resulted in no adverse effect on the microbial growth rate except that high concentrations of diclofenac exposure decreased the growth rate at SRT of 10 days. A significant increase in hydrolysis rate was determined in the diclofenac-acclimated biomass for both SRTs; even at high concentrations of diclofenac exposure, the hydrolysis rate remained unchanged. Long-term acclimation to diclofenac had a progressive impact on the hydrolysis kinetics, which could be attributed to an alteration in the microbial culture profile. Overall, the results suggest that the operation with diclofenac-acclimated biomass at higher SRTs could enrich a microbial culture capable of overcoming the adverse effect of the pollutant and improve the biodegradation potential as well.