Osteoblast proliferation on hydroxyapatite thin coatings produced by right angle magnetron sputtering

Right angle magnetron sputtering (RAMS) was used to produce hydroxyapatite (HA) film coatings on pure titanium substrates and oriented silicon wafer (Si(0 0 1)) substrates with flat surfaces as well as engineered surfaces having different forms. Analyses using synchrotron XRD, AFM, XPS, FTIR and SEM with EDS showed that as-sputtered thin coatings consist of highly crystalline hydroxyapatite. The HA coatings induced calcium phosphate precipitation when immersed in simulated body fluid, suggesting in vivo bioactive behavior. In vitro experiments, using murine osteoblasts, showed that cells rapidly adhere, spread and proliferate over the thin coating surface, while simultaneously generating strong in-plane stresses, as observed on SEM images. Human osteoblasts were seeded at a density of 2500 cells cm(-2) on silicon and titanium HA coated substrates by RAMS. Uncoated glass was used as a reference substrate for further counting of cells. The highest proliferation of human osteoblasts was achieved on HA RAMS-coated titanium substrates. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications.

Principles and potential of thermal hydrolysis of sewage sludge to enhance anaerobic digestion

Sewage sludge is rich source of carbon, nutrients, and trace elements and can be subjected to proper treatment before disposal to fulfill government legislation and protect receiving environments. Anaerobic digestion (AD) is a well-adopted technology for stabilizing sewage sludge and recovering energy-rich biogas and nutrient-rich digestate. However, a slow hydrolysis rate limits the biodegradability of sludge. In the present study we have attempted to explain the potential of thermal hydrolysis to enhance anaerobic digestion of sewage sludge. Thermal pretreatment improves biodegradability and recycling of the sludge as an excellent energy and nutrients recovery source at reasonable capital (CAPEX) and operational (OPEX) costs. Other pretreatments like conventional (below/above 100 °C), temperature-phased anaerobic digestion (TPAD), microwave and chemically mediated thermal pretreatment have also been accounted. This review provides a holistic overview of sludge's characterization and value-added properties, various techniques used for sludge pretreatment for resource recovery, emphasizing conventional and advanced thermal pretreatment, challenges in scale-up of these technologies, and successful commercialization of thermal pretreatment techniques.

Energy feasibility and life cycle assessment of sludge pretreatment methods for advanced anaerobic digestion

Energy sustainability is one of the critical parameters to be studied for the successful application of pretreatment processes. This study critically analyzes the energy efficiency of different energy-demanding sludge pretreatment techniques. Conventional thermal pretreatment of sludge (∼5% total solids, TS) produced 244 mL CH₄/gTS, which could result in a positive energy balance of 2.6 kJ/kg TS. However, microwave pretreatment could generate only 178 mL CH₄/gTS with a negative energy balance of -15.62 kJ/kg TS. In CAMBI process, the heat requirements can be compensated using exhaust gases and hot water from combined heat and power, and electricity requirements are managed by the use of cogeneration. The study concluded that <100 ℃ pretreatment effectively enhances the efficiency of anaerobic digestion and shows positive energy balance over microwave and ultrasonication. Moreover, microwave pretreatment has the highest global warming potential than thermal and ultrasonic pretreatments.

Semi-continuous anaerobic co-digestion of thermal and thermal-alkali processed organic fraction of municipal solid waste: Methane yield, energy analysis, anaerobic microbiome

The semi-continuous anaerobic co-digestion (AcoD) of thermal and thermal-alkali pretreated organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) was studied under varying hydraulic retention times (HRT) and organic loading rates (OLR Three semi-continuous digesters were operated under control (non-pre-treated), thermally pretreated (125 °C), and thermal-alkali pretreated (125°C-3g/L NaOH) conditions at variable OLRs at 2.5, 4.0, 5.1, and 7.6 kgVS/m3.d and corresponding HRTs of 30, 20, 15, and 10 days. The 10 and 43% higher methane yield (0.445 m3/kgVS) and 11 and 57% higher VS removal (52%) was achieved for thermal-alkali pretreated digester at 5.1 kgVS/m3.d OLR over thermally pretreated (0.408 m3/kgVS, 45% VS removal) and control digesters (0.310 m3/kgVS, 33% VS removal), respectively. Thermal and thermal-alkali digesters failed on increasing the OLR to 7.6 kgVS/m3.d, whereas the control digester becomes upset at 5.1 kgVS/m3.d OLR. The metagenomic study revealed that Firmicutes, Bacteroidetes, Chloroflexi, Euryarchaeota, Proteobacteria, and Actinobacteria were the predominant bacterial population, whereas Methanosarcina and Methanothrix dominated the archaeal community. Energy balance analysis revealed that thermal alkali pretreatment showed the highest positive energy balance of 114.6 MJ/ton with an energy ratio of 1.25 compared with thermally pretreated (81.5 MJ/ton) and control samples (-46.9 MJ/ton). This work pave the way for scaleup of both thermal and thermal-alkali pre-treatment at 125 °C to realize the techno-economic and energy potential of the process.

Construction of peptide conjugates with peptide nucleic acids containing an anthracene probe and their interactions with DNA

We designed and synthesized the peptide nucleic acid (PNA)-peptide conjugates having anthracene chromophores and investigated their interactions with calf thymus DNA, [d(AT)(10)](2), [d(GC)(10)](2), and [d(AT)(10)dA(6)](2). Considering the synthesis compatibility and expecting that a novel DNA analogue, PNA, can improve DNA binding properties of alpha-helix peptides, we attempted to attach thymine PNA oligomers at the C-terminus of a 14 amino acid alpha-helix peptide that contained a pair of artificial intercalators, anthracene, as a probe, and to examine their interactions with DNA using anthracene UV, fluorescence and circular dichroism properties. The results observed in this study showed that the designed peptide folded in an alpha-helix structure in the presence of calf thymus DNA, [d(AT)(10)](2), and [d(AT)(10)dA(6)](2) with the chromophores at the side-chain being fixed with a left-handed chiral-sense orientation. The alpha-helix and the anthracene signals were not observed for [d(GC)(10)](2). Incorporation of thymine PNA oligomers into the designed alpha-helix peptide increased the DNA binding ability to [d(AT)(10)dA(6)](2) with increasing the length of the PNA without changing the conformations of the peptide backbone and the anthracene side-chains.

Recalcitrant compounds formation, their toxicity, and mitigation: Key issues in biomass pretreatment and anaerobic digestion

Increasing energy demands and environmental issues have stressed the importance of sustainable methods of energy production. Anaerobic digestion (AD) of the biodegradable waste, i.e., agricultural residues, organic fraction of municipal solid waste (OFMSW), sewage sludge, etc., results in the production of biogas, which is a sustainable and cost feasible technique that reduces the dependence on fossil fuels and also overcomes the problems associated with biomass waste management. To solubilize the organic matter and enhance the susceptibility of hardly biodegradable fraction (i.e., lignocellulosic) for hydrolysis and increase methane production, several pretreatments, including physical, chemical, biological, and hybrid methods have been studied. However, these pretreatment methods under specific operating conditions result in the formation of recalcitrant compounds, such as sugars (xylose, Xylo-oligomers), organic acids (acetic, formic, levulinic acids), and lignin derivatives (poly and mono-phenolic compounds), causing significant inhibitory effects on anaerobic digestion. During the scaling up of these techniques from laboratory to industrial level, the focus on managing inhibitory compounds formed during pretreatment is envisaged to increase because of the need to use recalcitrant feedstocks in anaerobic digestion to increase biogas productivity. Therefore, it is crucial to understand the production mechanism of inhibitory compounds during pretreatment and work out the possible detoxification methods to improve anaerobic digestion. This paper critically reviews the earlier works based on the formation of recalcitrant compounds during feedstocks pretreatment under variable conditions, and their detrimental effects on process performance. The technologies to mitigate recalcitrant toxicity are also comprehensively discussed.

B cell responses to a peptide epitope. I. The cellular basis for restricted recognition

Primary humoral responses in BALB/c mice to a variety of peptide constructs containing a common 15-amino acid residue antigenic determinant (PS1) in conjunction with one or more Th cell epitopes were examined. In all cases, the mature IgG response was found to focus primarily on a tetrapeptide sequence, Asp-Pro-Ala-Phe. The dominance of this segment was independent of the position of the PS1 determinant in the peptide sequence and was also observed in constructs with a random secondary structure. In contrast to the mature IgG response, the early primary IgM response was constituted by multiple specificities that collectively spanned a major proportion of the PS1 sequence. However, subsequent progression of this response entailed a strict selection for only those Abs directed against the Asp-Pro-Ala-Phe segment and apparently occurred at or around the time of the IgM to IgG class switch. Studies of murine responses to peptide analogs containing single amino acid substitutions within the Asp-Pro-Ala-Phe sequence revealed that emergence of this segment as the dominant epitope was a consequence of active suppression of B cells directed against alternate determinants. Positive selection of this subset of Abs correlated with overall higher avidity for epitope binding and was the outcome of a competitive process enforced by the limiting amounts of Th cell help available in the early stages of the primary response.

B cell responses to a peptide epitope. I. The cellular basis for restricted recognition

Primary humoral responses in BALB/c mice to a variety of peptide constructs containing a common 15-amino acid residue antigenic determinant (PS1) in conjunction with one or more Th cell epitopes were examined. In all cases, the mature IgG response was found to focus primarily on a tetrapeptide sequence, Asp-Pro-Ala-Phe. The dominance of this segment was independent of the position of the PS1 determinant in the peptide sequence and was also observed in constructs with a random secondary structure. In contrast to the mature IgG response, the early primary IgM response was constituted by multiple specificities that collectively spanned a major proportion of the PS1 sequence. However, subsequent progression of this response entailed a strict selection for only those Abs directed against the Asp-Pro-Ala-Phe segment and apparently occurred at or around the time of the IgM to IgG class switch. Studies of murine responses to peptide analogs containing single amino acid substitutions within the Asp-Pro-Ala-Phe sequence revealed that emergence of this segment as the dominant epitope was a consequence of active suppression of B cells directed against alternate determinants. Positive selection of this subset of Abs correlated with overall higher avidity for epitope binding and was the outcome of a competitive process enforced by the limiting amounts of Th cell help available in the early stages of the primary response.

Advanced steam-explosion pretreatment mediated anaerobic digestion of municipal sludge: Effects on methane yield, emerging contaminants removal, and microbial community

Advanced steam explosion pretreatment, i.e., the Thermal hydrolysis process (THP) is applied mainly to improve the sludge solubilization and subsequent methane yield in the downstream anaerobic digestion (AD) process. However, the potential of THP in pretreating the high solids retention time (SRT) sludges, mitigating the risk of emerging organic micropollutants and effects on anaerobic microbiome in digester remains unclear. In this study, sludge from a sequencing batch reactor (SBR) system operating at a SRT of 40 days was subjected to THP using a 5 L pilot plant at the temperature ranges of 120-180 °C for 30-120 min. The effect of THP on organics solubilization, methane yield, organic micropollutant removal, and microbial community dynamics was studied. The highest methane yield of 507 mL CH4/g VSadded and volatile solids (VS) removal of 54% were observed at 160°C- 30min THP condition, i.e., 4.1 and 2.6 times higher than the control (123 mL CH4/gVSadded, 20.7%), respectively. The experimental values of hydrolysis coefficient and methane yield have been predicted using Modified Gompertz, First order, and Logistics models. The observed values fitted well with all three models showing an R2 value between 0.96 and 1.0. THP pretreated sludges showed >80% removal of Trimethoprim, Enrofloxacin, Ciprofloxacin, and Bezafibrate. However, Carbamazepine, 17α-ethinylestradiol, and Progesterone showed recalcitrant behavior, resulting in less than 50% removal. Microbial diversity analysis showed the dominance of Proteobacteria, Firmicutes, Chloroflexi, and Bacteroidetes, collectively accounting for >70-80% of bacterial reads. They are mainly responsible for the fermentation of complex biomolecules like polysaccharides, proteins, and lipids. The THP-mediated anaerobic digestion of sludge shows better performance than the control digestion, improved methane yield, higher VS and micropollutants removal, and a diverse microbiome in the digester.

Anaerobic digestion of thermal hydrolysis pretreated sludge: Process performance, metagenomic analysis, techno-economic and life cycle assessment

This study assessed the potential of thermal hydrolysis process (THP) combined with anaerobic digestion (AD) for high solids sewage sludge treatment across various hydraulic retention times (HRTs). Optimal performance was achieved at a 10-day HRT (6 kg VS/m3·day), yielding 408 L CH4/kg VS added and 54 % volatile solids (VS) removal under THP conditions of 160 °C, 30 min, and 6 bar pressure. Microbial analysis revealed predominant acetoclastic and hydrogenotrophic methanogens. Four scenarios were designed and analyzed for environmental and economic performance: Scenario 1 (conventional AD-CHP), Scenario 2 (conventional AD-BioCNG), Scenario 3 (THP AD-BioCNG), and Scenario 4 (THP AD-CHP). The results showed that scenarios with CHP integration achieved better environmental performance by generating sufficient energy to meet demand, with energy consumption as a key factor. Notably, scenario 4 had the lowest global warming potential (GWP) at -0.0185 kg CO2-eq, outperforming conventional AD (Scenario 1) with CHP, which had a GWP of -0.00232 kg CO2-eq. However, profitability analysis showed that Scenario 3 was the most economically viable, with a net present value (NPV) of $4.3 million, an internal rate of return (IRR) of 10.21 %, and a 17-year payback period. Although it had higher capital ($58 million) and operational costs ($12.5 million/year) than Scenario 4 ($45 million and $8.6 million/year), its greater biomethane yield resulted in higher revenue ($20.7 million/year), making it the most profitable option. While Scenario 4 offered the best environmental benefits, Scenario 3 emerged as the most financially sustainable choice. These findings highlight the environmental and economic advantage of utilizing THP-AD process over conventional AD, suggesting that THP-AD optimizes methane production, solids reduction, and environmental impact, making the Bio CNG pathway a sustainable and economically viable option.