Protein engineering of a nanoCLAMP antibody mimetic scaffold as a platform for producing bioprocess-compatible affinity capture ligands.

Protein A affinity chromatography is widely used for the large-scale purification of antibodies because of its high yield, selectivity, and compatibility with NaOH sanitation. A general platform to produce robust affinity capture ligands for proteins beyond antibodies would improve bioprocessing efficiency. We previously developed nanoCLAMPs (nano Clostridial Antibody Mimetic Proteins), a class of antibody mimetic proteins useful as lab-scale affinity capture reagents. This work describes a protein engineering campaign to develop a more robust nanoCLAMP scaffold compatible with harsh bioprocessing conditions. The campaign generated an improved scaffold with dramatically improved resistance to heat, proteases, and NaOH. To isolate additional nanoCLAMPs based on this scaffold, we constructed a randomized library of 1 × 1010 clones and isolated binders to several targets. We then performed an in-depth characterization of nanoCLAMPs recognizing yeast SUMO, a fusion partner used for the purification of recombinant proteins. These second-generation nanoCLAMPs typically had a Kd of <80 nM, a Tm of >70 °C, and a t1/2 in 0.1 mg/ml trypsin of >20 h. Affinity chromatography resins bearing these next-generation nanoCLAMPs enabled single-step purifications of SUMO fusions. Bound target proteins could be eluted at neutral or acidic pH. These affinity resins maintained binding capacity and selectivity over 20 purification cycles, each including 10 min of cleaning-in-place with 0.1 M NaOH, and remained functional after exposure to 100% DMF and autoclaving. The improved nanoCLAMP scaffold will enable the development of robust, high-performance affinity chromatography resins against a wide range of protein targets.

Soluble urate-induced effects on cytokine production in vitro - Assessment of methodologies and cell types.

BACKGROUND: Hyperuricemia has been shown to be an inducer of pro-inflammatory mediators by human primary monocytes. To study the deleterious effects of hyperuricemia, a reliable and stable in vitro model using soluble urate is needed. One recent report showed different urate-dissolving methods resulted in either pro-inflammatory or anti-inflammatory properties. The aim of this study was to compare the effect of two methods of dissolving urate on both primary human peripheral blood mononuclear cells (PBMCs) and THP-1 cells. The two methods tested were 'pre-warming' and 'dissolving with NaOH'. METHODS: Primary human PBMCs and THP-1 cells were exposed to urate solutions, prepared using the two methodologies: pre-warming and dissolving with NaOH. Afterwards, cells were stimulated with various stimuli, followed by the measurement of the inflammatory mediators IL-1ß, IL-6, IL-1Ra, TNF, IL-8, and MCP-1. RESULTS: In PBMCs, we observed an overall pro-inflammatory effect of urate, both in the pre-warming and the NaOH dissolving method. A similar pro-inflammatory effect was seen in THP-1 cells for both dissolving methods after restimulation. However, THP-1 cells exhibited pro-inflammatory profile with exposure to urate alone without restimulation. We did not find MSU crystals in our cellular assays. CONCLUSIONS: Overall, the urate dissolving methods do not have critical impact on its inflammatory properties. Soluble urate prepared using either of the two methods showed mostly pro-inflammatory effects on human primary PBMCs and monocytic cell line THP-1. However, human primary PBMCs and the THP-1 differ in their response to soluble urate without restimulation.

Comparative analysis of Escherichia coli Nissle 1917 ghosts quality: a study of two chemical methods.

The gram-negative bacterium Escherichia coli Nissle 1917 (EcN) has long been recognized for its therapeutic potential in treating various intestinal diseases. Bacterial ghosts (BGs) are empty shells of non-living bacterial cells that demonstrate enormous potential for medicinal applications. Genetic and chemical techniques can create these BGs. In the current study, we produced Escherichia coli Nissle 1917 ghosts (EcNGs) for the first time using benzoic acid (BA) and sodium hydroxide (SH). BA is a feeble acidic chemical that enhances gram-negative bacteria's external membrane permeability, reduces energy production, and decreases internal pH. SH has shown success in producing BGs from some gram-negative and gram-positive organisms. This research aims to produce EcNGs using the minimum inhibitory concentration (MIC) of SH and BA, specifically 3.125 mg/mL. We assessed the bacterial quality of the BGs produced using quantitative PCR (qPCR) and Bradford protein assays. Field emission scanning electron microscopy (FE-SEM) showed the three-dimensional structure of EcNGs. The study confirmed the presence of tunnel-like pores on the outer surface, indicating the preservation of cell membrane integrity. Importantly, this investigation introduces BA as a novel chemical inducer of EcNGs, suggesting its potential alongside SH for efficient EcNG formation.

CO2-Mediated Alkali-Neutralization Curdlan Hydrogels for Potential Wound Healing Application.

Physical hydrogels of natural polysaccharides are considered as ideal candidates for wound dressing due to their natural biological activity and no harmful cross-linking agents. However, it remains a challenge to fabricate such hydrogel dressings in a facile and low-cost way. Herein, we reported an easy and cost-effective method to construct CO2-mediated alkali-neutralization Curdlan (CR) hydrogels without using an external cross-linking agent. Two types of hydrogels (denoted as CR-NaOH and CR-Na3PO4, respectively) were fabricated by dissolving CR powders in a NaOH or Na3PO4 aqueous solution, followed by keeping the CR alkaline solutions in air. The obtained pure CR hydrogels possessed a tunable porous structure with walls containing different forms of nanofibrils. These hydrogels exhibited much higher gel strength by comparison with the gels prepared by conventional heating treatment. They were flexible, stretchable, twistable, and conformable to arbitrarily curved skins. Moreover, they exhibited ideal swellability, proper degradability, and water vapor transmission rate, and their physicochemical properties were closely related to CR concentration in the alkaline solution. These two hydrogels also supported the growth of L929 cells. Importantly, studies on wound healing revealed that both 3CR-NaOH and 3CR-Na3PO4 hydrogels were capable of accelerating the wound healing process through recruiting more macrophages/fibroblasts, inducing more collagen deposition and neovascularization (α-SMA and CD31) without carrying any exogenous bioactive components. In conclusion, the present work not only reported promising materials for application in wound therapy but also offered a facile and safe manufacturing procedure for generating pure CR physical hydrogels with better performance.

Impact of NaOH based perfusion-decellularization protocol on mechanical resistance of structural bone allografts.

INTRODUCTION: To mitigate the post-operative complication rates associated with massive bone allografts, tissue engineering techniques have been employed to decellularize entire bones through perfusion with a sequence of solvents. Mechanical assessment was performed in order to compare conventional massive bone allografts and perfusion/decellularized massive bone allografts. MATERIAL AND METHODS: Ten porcine femurs were included. Five were decellularized by perfusion. The remaining 5 were left untreated as the "control" group. Biomechanical testing was conducted on each bone, encompassing five different assessments: screw pull-out, 3-points bending, torsion, compression and Vickers indentation. RESULTS: Under the experimental conditions of this study, all five destructive tested variables (maximum force until screw pull-out, maximum elongation until screw pull-out, energy to pull out the screw, fracture resistance in flexion and maximum constrain of compression) were statistically significantly superior in the control group. All seven nondestructive variables (Young's modulus in flexion, Young's modulus in shear stress, Young's modulus in compression, Elastic conventional limit in compression, lengthening to rupture in compression, resilience in compression and Vickers Hardness) showed no significant difference. DISCUSSION: Descriptive statistical results suggest a tendency for the biomechanical characteristics of decellularized bone to decrease compared with the control group. However, statistical inferences demonstrated a slight significant superiority of the control group with destructive mechanical stresses. Nondestructive mechanical tests (within the elastic phase of Young's modulus) were not significantly different.

Agrocybe cylindracea Dietary Fiber Modification: Sodium Hydroxide Treatment Outperforms High-Temperature, Cellulase, and Lactobacillus Fermentation.

Agrocybe cylindracea dietary fiber (ADF) contains 95% water-insoluble dietary fiber, resulting in poor application performance. To address this issue, ADF was modified by four methods (cellulase, sodium hydroxide, high-temperature, and Lactobacillus fermentation) in this paper. By comparing the physicochemical properties, microstructures, monosaccharide compositions, and functional characteristics (antioxidant and α-glucosidase inhibitory activities in vitro) of all modified ADF samples, the optimal modification method was selected. Results showed that sodium hydroxide treatment was deemed the most effective modification method for ADF, as alkali-treated ADF (ADF-A) revealed a higher oil-holding capacity (2.02 g/g), swelling capacity (8.38 mL/g), cholesterol adsorption (6.79 mg/g), and α-glucosidase inhibitory activity (more than 70% at 0.4-0.6 mg/mL) than the other modified samples. The looser microstructure in ADF-A might be attributed to molecular rearrangement and spatial structure disruption, which resulted in smaller molecular sizes and decreased viscosity, hence improving ADF's physicochemical and functional qualities. All these findings indicate the greater application potential of modified ADF products in food and weight-loss industries, providing a comprehensive reference for the industrial application of ADF.

Alkaline stress inhibits the growth of Staphylococcus epidermidis by inducing TCA cycle-triggered ROS production.

Many species of bacteria interact on the human skin to form a certain microbiome. Delftia acidovorans, a bacterium detected from human skin, inhibits the growth of S. epidermidis, a dominant bacterium of the human skin microbiota. Here, we show that ammonia secreted by D. acidovorans inhibits the growth of S. epidermidis by increasing the pH value of the medium. The pH value of D. acidovorans culture supernatant (CS) was higher than that of the medium without culture. The inhibitory activity of the D. acidovorans CS against the growth of S. epidermidis was decreased by neutralization with hydrochloric acid. Genes encoding enzymes related to ammonia production were found in the D. acidovorans genome. Moreover, the D. acidovorans CS contained a high concentration of ammonia. The addition of ammonia to S. epidermidis culture led to an increase in the reactive oxygen species (ROS) production and inhibited S. epidermidis growth. The addition of sodium hydroxide also led to an increase in the ROS production and inhibited S. epidermidis growth. The inhibitory activity of ammonia and sodium hydroxide against S. epidermidis growth was suppressed by malonic acid, an inhibitor of succinate dehydrogenase in the tricarboxylic acid (TCA) cycle, and N-acetyl-l-cysteine, a free radical scavenger. These findings suggest that D. acidovorans secretes ammonia and alkaline stress inhibits the growth of S. epidermidis by inducing TCA cycle-triggered ROS production.

Unexpected Complexity in the Products Arising from NaOH-, Heat-, Amine-, and Glycosylase-Induced Strand Cleavage at an Abasic Site in DNA.

Hydrolytic loss of nucleobases from the deoxyribose backbone of DNA is one of the most common unavoidable types of damage in synthetic and cellular DNA. The reaction generates abasic sites in DNA, and it is important to understand the properties of these lesions. The acidic nature of the α-protons of the ring-opened abasic aldehyde residue facilitates the ß-elimination of the 3'-phosphoryl group. This reaction is expected to generate a DNA strand break with a phosphoryl group on the 5'-terminus and a trans-α,ß-unsaturated aldehyde residue on the 3'-terminus; however, a handful of studies have identified noncanonical sugar remnants on the 3'-terminus, suggesting that the products arising from strand cleavage at apurinic/apyrimidinic sites in DNA may be more complex than commonly thought. We characterized the strand cleavage induced by the treatment of an abasic site-containing DNA oligonucleotide with heat, NaOH, piperidine, spermine, and the base excision repair glycosylases Fpg and Endo III. The results showed that under multiple conditions, cleavage at an abasic site in a DNA oligomer generated noncanonical sugar remnants including cis-α,ß-unsaturated aldehyde, 2-deoxyribose, and 3-thio-2,3-dideoxyribose products on the 3'-terminus of the strand break.

Mechanistic studies of dinucleotide and oligonucleotide model cyclobutane pyrimidine dimer (CPD) DNA lesions under alkaline conditions.

Cyclobutane pyrimidine dimers (CPDs) are the most abundant mutagenic DNA lesions formed in mammalian cells upon exposure to UV-B radiation (280-315 nm) in sunlight. These lesions are thought to be chemically stable and to withstand high concentrations of acids and bases.While earlier investigations of DNA lesions containing saturated pyrimidines have shown that the C4 carbonyl is a potential target of nucleophilic attack, similar reactions with thymine nucleobase model CPDs clearly showed that the cis-syn CPD (major isomer) is stable in the presence of a high concentration of alkali at room temperature. Here is described the alkaline reactivity of these lesions when contained within a dinucleotide CPD model system. Results using cis-syn CPD formed from dinucleotide 5'-TpT-3' combined with [18O]-labelling indicated that CPD undergoes a water addition at the C4=O groups of these now saturated rings. The intermediate formed, however, completely reverts to the starting lesion. Along with confirming the target of water addition within CPD lesions, it was also determined that the two C4 carbonyls present on adjacent saturated pyrimidine rings of the photolesion undergo water exchange at different rates (3' > 5'). Moreover, the difference in reactivity exhibited by these two positions is not limited to a dinucleotide and was observed also in oligonucleotides. Overall, a full understanding of the chemistry of CPD lesions is crucial to our knowledge of naturally-occuring DNA modifications and may lead to further insight into their detection, modification, and biochemical recognition & repair.

Chemical composition and in situ degradability of sugarcane tip hay subjected to alkaline treatment.

The present study aimed to evaluate the effect of alkaline treatments with urea, NaOH and Ca(OH)2 on chemical composition and in situ ruminal degradability of dry matter, crud protein and neutral detergent fiber of sugarcane tip hay. Samples were incubated in the rumen of three cannulated cattle for up to 72 hours in a split plot randomized block design. Ammoniation with 6% urea increased (p<0.05) the crude protein content by 13% and reduced the neutral detergent fiber and insoluble nitrogen content of the hay. When treated with the highest doses of the compounds, there was a high potential degradability of dry matter, crude protein and neutral detergent fiber, and a shorter neutral detergent fiber lag time. Ammoniation with urea promotes a reduction in the content of NDF, hemicellulose and insoluble nitrogen, with an increase in the content of CP in the hay, with emphasis for the level of 6% urea. The ruminal degradation of sugarcane tip hay increases with alkaline treatments using 6% urea or 3% NaOH, however, ammoniation with urea is indicated for the treatment of hay, as this is low cost and can be easily adopted by farmers in the semiarid region.

Effect of Tauroursodeoxycholic Acid on Inflammation after Ocular Alkali Burn.

Inflammation is the main cause of corneal and retinal damage in an ocular alkali burn (OAB). The aim of this study was to investigate the effect of tauroursodeoxycholic acid (TUDCA) on ocular inflammation in a mouse model of an OAB. An OAB was induced in C57BL/6j mouse corneas by using 1 M NaOH. TUDCA (400 mg/kg) or PBS was injected intraperitoneally (IP) once a day for 3 days prior to establishing the OAB model. A single injection of Infliximab (6.25 mg/kg) was administered IP immediately after the OAB. The TUDCA suppressed the infiltration of the CD45-positive cells and decreased the mRNA and protein levels of the upregulated TNF-α and IL-1ß in the cornea and retina of the OAB. Furthermore, the TUDCA treatment inhibited the retinal glial activation after an OAB. The TUDCA treatment not only ameliorated CNV and promoted corneal re-epithelization but also attenuated the RGC apoptosis and preserved the retinal structure after the OAB. Finally, the TUDCA reduced the expression of the endoplasmic reticulum (ER) stress molecules, IRE1, GRP78 and CHOP, in the retinal tissues of the OAB mice. The present study demonstrated that the TUDCA inhibits ocular inflammation and protects the cornea and retina from injury in an OAB mouse model. These results provide a potential therapeutic intervention for the treatment of an OAB.

Re-endothelialization of non-detergent decellularized porcine vessels.

Tissue engineering utilizes an interdisciplinary approach to generate constructs for the treatment and repair of diseased organs. Generation of small vessels as vascular grafts or as envisioned central vessel for vascularized constructs is still a challenge. Here, the decellularization of porcine vessels by a non-detergent based protocol was developed and investigated. Perfusion-decellularization with sodium hydroxide solution resulted in removal of cellular material throughout the whole length of the vessel while preserving structural and mechanical integrity. A re-endothelialization of the retrieved matrix with human umbilical vein endothelial cells and cardiac endothelial cells was achieved through rotation-based seeding employing a custom-made bioreactor. A confluent monolayer was detected on the entire luminal surface. Thus, a non-detergent-based decellularization method allowing the re-endothelialization of the luminal surface was developed in this study, thereby paving the way for future implementation of the resulting construct as vascular graft or as central vessel for tissue engineered constructs in need of a perfusion system with readily available anastomosis sites.

A practicable method to prepare nitrated proteins with peroxynitrite and low concentration of sodium hydroxide.

Peroxynitrite is an ion acting as a powerful oxidant and nucleophile, which plays a key role in the inflammation and aging process by nitrating tyrosine or tryptophan residues of the proteins. Nitration of a target protein is considered to be a proper method to study the behavioral change of the proteins being nitrated. The commonly used methods for peroxynitrite preparation in vitro usually contain high concentration of sodium hydroxide, which easily induces hydrolysis of target proteins. Accordingly, the method for peroxynitrite preparation was optimized in vitro by changing the sequence of hydrochloric acid and sodium hydroxide added. After different amount of hydrochloric acid added to the system following sodium nitrite, peroxynitrite can be yielded in a concentration up to 60 mM with sodium hydroxide as low as 17 mM. More importantly, biological activity of the target protein was well maintained after protein nitration since low sodium hydroxide was used.

Biogas Production from Physicochemically Pretreated Grass Lawn Waste: Comparison of Different Process Schemes.

Various pretreatment methods, such as thermal, alkaline and acid, were applied on grass lawn (GL) waste and the effect of each pretreatment method on the Biochemical Methane Potential was evaluated for two options, namely using the whole slurry resulting from pretreatment or the separate solid and liquid fractions obtained. In addition, the effect of each pretreatment on carbohydrate solubilization and lignocellulossic content fractionation (to cellulose, hemicellulose, lignin) was also evaluated. The experimental results showed that the methane yield was enhanced with alkaline pretreatment and, the higher the NaOH concentration (20 g/100 gTotal Solids (TS)), the higher was the methane yield observed (427.07 L CH4/kg Volatile Solids (VS), which was almost 25.7% higher than the BMP of the untreated GL). Comparing the BMP obtained under the two options, i.e., that of the whole pretreatment slurry with the sum of the BMPs of both fractions, it was found that direct anaerobic digestion without separation of the pretreated biomass was favored, in almost all cases. A preliminary energy balance and economic assessment indicated that the process could be sustainable, leading to a positive net heat energy only when using a more concentrated pretreated slurry (i.e., 20% organic loading), or when applying NaOH pretreatment at a lower chemical loading.

Effect of alkaline and sonication pretreatments on the rumen degradability of date palm seeds.

The main objective of this research was to evaluate the effects of chemical treatment and sonication (ultrasound) processing on the fiber composition and rumen degradability of date palm seeds (DPS). In the first trial, the effects of incubation or sonication in 4% sodium hydroxide (NaOH) on DPS fiber content and ruminal degradability were evaluated. Relative to untreated seeds, the ruminal degradability of DPS neutral detergent fiber (NDF) and organic matter (OM) increased (P < 0.05) for the treated seeds and were highest (P < 0.05) for the sonicated seeds. Relative to untreated seeds, the hemicellulose and lignin content were lower (P < 0.05) for the sonicated seeds, while the cellulose content was higher (P < 0.05) for the incubated seeds. In the second trial, the effects of subjecting DPS to different sonication times (5, 10, 20, and 30 min) were evaluated. The degradability of seeds' NDF and OM were greater (P < 0.05) for the sonicated than unsonicated seeds. The highest NDF degradability was seen after 30 min sonication, whereas the OM degradability was not affected by sonication time (P > 0.05). In the third trial, the effects of subjecting DPS to sonication in different NaOH solutions (1%, 2%, 4% NaOH) were evaluated. Relative to untreated seeds, the rumen degradability of seeds' NDF and OM increased with all NaOH concentrations but was highest (P < 0.05) with the 4% NaOH. In conclusion, our results showed that treating DPS with 4% NaOH increased the seeds' ruminal degradability, and subjecting DPS to sonication further improved their degradability in the rumen.

Optimization of hydrogel containing toluidine blue O for photodynamic therapy in treating acne.

Antibiotics and photodynamic therapy (PDT) are widely employed in curing acne. However, antibiotics as an effective treatment would lead to bacterial resistance and severe side effects. In this study, we aimed to develop a novel TBO hydrogel, which could prolong the retention time of photosensitizer (TBO) at the lesion site and improve therapeutic effect. In vitro antibacterial experiments (against Staphylococcus aureus and Escherichia coli), the response surface methodology was used to optimize the formulation of TBO hydrogel. The results indicated that the optimal formulation was 0.5% (v/v) carbomer, 0.01 mg/mL TBO, 0.5% (v/v) ethanol concentration, 0.5% (v/v) Tween 80, the mass ratio of NaOH to carbomer of 0.4 (w/w). The TBO hydrogel formulation showed the strong antibacterial activity for Propionibacterium acnes. The stability, pH, and antibacterial activity of TBO hydrogel did not significantly change under 4 °C, 25 °C, and 40 °C during 6-week storage. Furthermore, TBO combined with carbomer hydrogel showed the 51.28% (4 h) and 69.80% (24 h) release. In summary, the hydrogel TBO might be a vital therapeutic strategy to promote the PDT applied in the topical therapy of acne. Graphical abstract A TBO hydrogel for photodynamic therapy in the treatment of acne.

Decellularized and Secured Porcine Arteries with NaOH-based Process: Proof of Concept.

BACKGROUND: There is a need for small caliber vascular prosthesis. Synthetic grafts are hindered by thrombogenicity and rapid occlusion. Decellularized matrices could be an alternative. We assessed in vitro and in vivo the biocompatibility of porcine artery treated with a chemical/physical process for decellularization and graft securitization with non/conventional pathogens inactivation. METHODS: Porcine carotid arteries (PCA) were treated. First, biopsies (n = 4/tissue) were performed before/after treatment to assess decellularization (hematoxylin and eosin/-4',6-diamidino-2-phenylindole/DNA/Miller). Second, 5 rats received an abdominal aortic patch of decellularized PCA (DPCA). Four pigs received subcutaneous DPCA implants (n = 2/pig). Half were explanted at day 15 and half at day 30. Finally, 2 pigs received DPCA (n = 2) and polytetrafluoroethylene prosthesis (n = 1), respectively, as carotid interposition. Implants were removed at day 30. Inflammation (CD3 and CD68 immunostaining) calcifications (von Kossa staining), remodeling (hematoxylin and eosin), and vascular characterization (CD31 and alpha-smooth muscle actin immunofluorescent staining) were investigated. RESULTS: Ninety-five percentage of decellularization was obtained without structural deterioration. No death occurred. Low inflammatory reaction was found in the 2 models for DPCA. Acquisition of vascular identity was confirmed in the rodent and porcine models. Similarity between native PCA and DPCA was observed after 30 days. In contrast, polytetrafluoroethylene graft showed severe calcifications, higher CD3 reaction, and higher intimal hyperplasia (P < 0.05). CONCLUSIONS: The physical and chemical process ensures decellularization of carotid porcine arteries and their in vivo remodeling with the presence of an endothelium and smooth-muscle-like cells as well as a low level of inflammatory cells.

Improved exogenous DNA uptake in bovine spermatozoa and gene expression in embryos using membrane destabilizing agents in ICSI-SMGT.

Sperm-mediated gene transfer (SMGT) is a simple, fast, and economical biotechnological tool for producing transgenic animals. However, transgene expression with this technique in bovine embryos is still inefficient due to low uptake and binding of exogenous DNA in spermatozoa. The present study evaluated the effects of sperm membrane destabilization on the binding capacity, location and quantity of bound exogenous DNA in cryopreserved bovine spermatozoa using Triton X-100 (TX-100), lysolecithin (LL) and sodium hydroxide (NaOH). Effects of these treatments were also evaluated by intracytoplasmic sperm injection (ICSI)-SMGT. Results showed that all treatments bound exogenous DNA to spermatozoa including the control. Spermatozoa treated with different membrane destabilizing agents bound the exogenous DNA throughout the head and tail of spermatozoa, compared with the control, in which binding occurred mainly in the post-acrosomal region and tail. The amount of exogenous DNA bound to spermatozoa was much higher for the different sperm treatments than the control (P < 0.05), most likely due to the damage induced by these treatments to the plasma and acrosomal membranes. Exogenous gene expression in embryos was also improved by these treatments. These results demonstrated that sperm membrane destabilization could be a novel strategy in bovine SMGT protocols for the generation of transgenic embryos by ICSI.

Comparison and analysis of several wet scrubbing solutions to remove methyl mercaptan.

Wet scrubbing is regarded as an effective method to remove hydrophobic organic odorants. The focus of wet scrubbing is to choose an appropriate scrubbing liquid. In this study, methyl mercaptan (CH3SH) was selected as a representative hydrophobic organic odorant for treatment by wet scrubbing using several types of scrubbing solution: ethanol (C2H5OH), lead acetate ((CH3COO)2Pb), sodium hypochlorite (NaClO), and sodium hydroxide (NaOH). A comparative analysis of the treatment efficiency, operation cost, and environmental impact was conducted. Results of the technical and economic comparison indicate that the C2H5OH solution is the best choice of scrubbing solution among those tested. These findings serve as a reference for engineering design and operation for the removal of hydrophobic organic odorants.

Environmental evaluation of flocculation efficiency in the separation of the microalgal biomass of Scenedesmus sp. cultivated in full-scale photobioreactors.

In this paper the environmental evaluation of the separation process of the microalgal biomass Scenedesmus sp. from full-scale photobioreactors was carried out at the Research and Development Nucleus for Sustainable Energy (NPDEAS), with different flocculants (iron sulfate - FeCl3, sodium hydroxide - NaOH, calcium hydroxide - Ca(OH)2 and aluminum sulphate Al2(SO4)3, by means of the life cycle assessment (LCA) methodology, using the SimaPro 7.3 software. Furthermore, the flocculation efficiency by means of optical density (OD) was also evaluated. The results indicated that FeCl3 and Al2(SO4)3 were highly effective for the recovery of microalgal biomass, greater than 95%. Though, when FeCl3 was used, there was an immediate change in color to the biomass after the orange colored salt was added, typical with the presence of iron, which may compromise the biomass use according to its purpose and Al2(SO4)3 is associated with the occurrence of Alzheimer's disease, restricting the application of biomass recovered through this process for nutritional purposes, for example. Therefore, it was observed that sodium hydroxide is an efficient flocculant, promoting recovery around 93.5% for the ideal concentration of 144 mg per liter. It had the best environmental profile among the compared flocculant agents, since it did not cause visible changes in the biomass or compromise its use and had less impact in relation to acidification, eutrophication, global warming and human toxicity, among others. Thus, the results indicate that it is important to consider both flocculation efficiency aspects and environmental impacts to identify the best flocculants on an industrial scale, to optimize the process, with lower amount of flocculant and obtain the maximum biomass recovery and decrease the impact on the extraction, production, treatment and reuse of these chemical compounds to the environment. However, more studies are needed in order to evaluate energy efficiency of the process coupled with other microalgal biomass recovery technologies. In addition, studies with natural flocculants, other polymers and changes in pH are also needed, as these are produced in a more sustainable way than synthetic organic polymers and have the potential to generate a biomass free of undesirable contaminants.