Chemical and Biomolecular Engineering - Research Publications

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    Financial and environmental impacts of using oxygen rather than air as a ventilator drive gas
    Balmaks, E ; Kentish, SE ; Seglenieks, R ; Lee, JH ; McGain, F (WILEY, 2022-12)
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    The effect of pH on the fat and protein within cream cheese and their influence on textural and rheological properties
    Ong, L ; Pax, AP ; Ong, A ; Vongsvivut, J ; Tobin, MJ ; Kentish, SE ; Gras, SL (Elsevier BV, 2020-12-01)
    The effect of variation in acid gel pH during cream cheese production was investigated. The gel microstructure was denser and cheese texture firmer, as the pH decreased from pH 5.0 to pH 4.3, despite the viscoelasticity of these gels remaining similar during heating. Protein hydration and secondary structure appeared to be key factors affecting both cheese microstructure and properties. Proteins within the matrix appeared to swell at pH 5.0, leading to a larger corpuscular structure; greater β-turn structure was also observed by synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy and the cheese was softer. A decrease in pH led to a denser microstructure with increased aggregated β-sheet structure and a firmer cheese. The higher whey protein loss at low pH likely contributed to increased cheese hardness. In summary, controlling the pH of acid gel is important, as this parameter affects proteins in the cheese, their secondary structure and the resulting cream cheese.
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    Effects of shredding on the functionality, microstructure and proteolysis of low-moisture mozzarella cheese
    Pax, AP ; Ong, L ; Kentish, SE ; Gras, SL (ELSEVIER SCI LTD, 2021-06)
    Low-moisture mozzarella cheese (LMMC) is commonly shredded before packaging, however, the effects of shredding are not fully understood. Industrially-produced block and shredded LMMC were studied during 8 weeks of storage at 4 °C. Cheese shredded on 15 d and at 8 weeks of age, coated with microcrystalline cellulose and stored in a modified atmosphere (70% N₂ and 30% CO₂), had an altered microstructure after 8 weeks compared with vacuum-packed block cheese. In the latter case the fat formed a more dispersed phase. Proteolysis was higher in shredded samples and a higher level of two bacterial proteases was detected. Despite these differences, the meltability and stretchability of the block and shredded LMMC were similar. The microstructure and functionality of cheese shredded at 15 d and stored for a further 6 weeks was similar to cheese shredded at 8 weeks, suggesting there is a flexible period for performing cheese shredding processes.
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    Structure and functionality of almond proteins as a function of pH
    Devnani, B ; Ong, L ; Kentish, S ; Gras, SL (ELSEVIER, 2021-10)
    Almond proteins have potential utility in a range of food and beverages but it is not clear how pH affects protein structure and function. The behaviour of almond protein isolate was examined under conditions of neutral and acidic pH (pH 7 and 4). The isolate was highly soluble (70–80%) at either pH. An increase in acidity lead to protein unfolding, an increase in random coil structure and the appearance of lower molecular weight proteins due to acidic hydrolysis. These structural changes at pH 4 increased the capacity for foam formation and foam stability, increased viscosity and led to concentration and age dependent thickening. Gels, similar in strength but with distinct microstructures and properties were obtained following heating. At pH 7, a particulate type gel with an interconnected protein network was formed, while the gel at pH 4 had a dense continuous protein matrix. The gels differed in their susceptibility to chemical disruption, suggesting different underlying molecular interactions. The ability to alter protein structure and properties as a function of pH and heating could be used to broaden the application of almond proteins and develop a variety of food products, such as protein supplements and vegan alternatives to traditional products.
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    Pilot scale concentration of cheese whey by forward osmosis: A short-cut method for evaluating the effective pressure driving force
    Artemi, A ; Chen, GQ ; Kentish, SE ; Lee, J (Elsevier, 2020-11-01)
    Cheese whey was concentrated to a concentration factor of 2.7 in a pilot scale forward osmosis filtration system, using a commercial cellulose triacetate membrane in a spiral-wound configuration. The whey was concentrated in a batch mode, using sodium chloride as the draw solution at initial osmotic pressures of 53–75 bar. During the process, flux was shown to reduce due to the simultaneous decrease in the bulk osmotic pressure of the draw solution, increase in the bulk osmotic pressure of the whey and the effect of concentration polarisation on both sides of the membrane. The flux is known to be driven by the effective osmotic pressures of whey and the draw solution on the surface of the membrane active layer. A short-cut approach that requires minimal information in advance about the osmotic pressure of whey and the geometry of the filtration system was implemented, enabling the determination of these effective osmotic pressures. The results obtained were shown to be in agreement with the fundamental forward osmosis flux model. The short-cut approach can be utilised for estimating effective osmotic pressures of other liquid food streams to be concentrated by forward osmosis, without the need of external measurements.
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    The relevance of critical flux concept in the concentration of skim milk using forward osmosis and reverse osmosis
    Artemi, A ; Chen, GQ ; Kentish, SE ; Lee, J (Elsevier BV, 2020-10-01)
    Skim milk was concentrated at 10 °C using forward osmosis (FO), reverse osmosis (RO) and pressure-assisted forward osmosis (PAFO). A pressure of 40 bar, in the form of draw solution osmotic pressure (FO and PAFO modes) or transmembrane hydraulic pressure (RO mode) was applied; an additional hydraulic pressure of 2 bar was applied in the PAFO mode. More severe protein fouling was observed in RO, followed by PAFO and then FO. This was credited to the difference in the initial permeate flux, induced by the different effective driving pressures, with RO having a greater deviation of the initial flux from the critical flux value. The critical flux was determined for the FO and RO modes using a step-wise increase of draw solution osmotic pressure or hydraulic pressure, at a constant milk solids content. The critical flux was between 5.4 L/m2h (1.5 × 10−6 m3/m2s) and 7.2 L/m2h (2 × 10−6 m3/m2s) for both the FO and RO modes at a cross flow velocity of 0.2 m/s. The similarities in the critical flux for FO and RO suggests that the critical flux does not depend on the nature of pressure applied on the system (hydraulic or osmotic). Therefore, when operated at the same flux and crossflow velocity, FO would not fundamentally provide a lower fouling environment compared to RO. An increase of the solids content from 8.7% to 17.3% caused a reduction in the critical flux from 5.4 L/m2h to 3.1 L/m2h (8.5 × 10−7 m3/m2s).
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    Evaporation reduction and salinity control in microalgae production ponds using chemical monolayers
    Poddar, N ; Scofield, J ; Shi, S ; Prime, EL ; Kentish, SE ; Qiao, GG ; Martin, GJO (ELSEVIER, 2022-07)
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    Assessment of Membrane Performance for Post-Combustion CO2 Capture
    Liu, L ; Lee, JH ; Han, SH ; Ha, SY ; Chen, GQ ; Kentish, SE ; Yeo, J-G (AMER CHEMICAL SOC, 2022-01-12)
    This work investigates the separation performance of a commercial carbonized polyimide hollow fiber membrane module for post-combustion CO2 capture applications. In particular, the resilience to water and sulfur and nitrogen oxides (SOx and NOx) as gas impurities was examined. The membrane exhibited a CO2 permeance of 660 Gas Permeance Units (GPU) and a CO2/N2 permselectivity of 20 at 50 °C when the permeate side was controlled at 0.2 bar absolute pressure. With an increase in water vapor in the feed stream, this CO2 permeance decreased slightly, while the CO2/N2 selectivity increased slightly, due to the combination of competitive sorption and concentration polarization. The water vapor permeance was high, which made accurate measurement difficult due to the concentration polarization but a value of 1090 ± 200 GPU was recorded. The membrane was then examined under three mixed gas conditions (i.e. SO2/CO2/O2/N2, NO/CO2/N2, and NO/NO2/N2) for a time frame of 30 days. The permeances of SO2, O2, NO, and NO2 were 650 ± 50, 155 ± 5, 125 ± 10, and 70 ± 5 GPU at 30 °C, respectively. All of these minor components had a marginal impact on the membrane separation performance during the testing period, indicating strong commercial potential. The higher permeance of SO2 and NO relative to nitrogen meant that these penetrants were concentrated in the permeate stream, which might lead to issues with downstream corrosion in a humid environment. Conversely, the permeance of NO2 was low.
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    Bioactives from Whey: A Sustainable Approach to Enzymatic Production of Sialyl-N-acetyllactosamine
    Alavijeh, MK ; Zeuner, B ; Meyer, AS ; Gras, SL ; Kentish, SE (AMER CHEMICAL SOC, 2022-05-16)
    The use of dairy whey to manufacture pharmaceutical products fosters sustainable environmental and economic development. This study represents a new strategy for upgrading of whey to 3′-sialyl-N-acetyllactosamine (3′-SLN) as an important structural component of glycoproteins and a receptor analog capable of forming complexes with hemagglutinins on influenza viruses. N-Acetyllactosamine (LacNAc) was enzymatically produced and purified directly from whey with no pretreatment required. An engineered and recombinantly produced sialidase with trans-sialylation ability from the non-pathogenic Trypanosoma rangeli was then used to transfer sialic acid from whey-derived, sialylated casein glycomacropeptide (CGMP) to this LacNAc. A maximum of 0.92 mM 3′-SLN was obtained at an equimolar ratio of LacNAc to bound sialic acid in CGMP; on the other hand, a molar ratio of 10 gave a fourfold greater 3′-SLN concentration. The variations in the concentration of 3′-SLN and free sialic acid during the hydrolysis reaction were modeled under different reaction conditions using machine learning and mechanistic approaches. The mechanistic analysis of the reaction indicated that the relative initial trans-sialylation rate to hydrolysis rate is directly proportional to the initial LacNAc concentration, with the ratio of trans-sialylation to hydrolysis rate constants equal to 111 M-1. The maximum 3′-SLN yield obtained was 75% based on α-2,3-sialic acid bound to CGMP. Separation of CGMP and reuse of enzyme were also investigated in an enzymatic membrane reactor.
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    The impact of water, BTEX compounds and ethylene glycol on the performance of perfluoro(butenyl vinyl ether) based membranes for CO2 capture from natural gas
    El-Okazy, MA ; Liu, L ; Zhang, Y ; Kentish, SE (ELSEVIER, 2022-07-15)
    Glassy perfluoropolymers offer a remarkable resistance towards many species that can alter the separation performance of conventional polymeric membranes. In this study, the performance of Cytop® and CyclAFlor™ random copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD) are studied for the first time for carbon dioxide capture in the presence of impurities that are common in raw natural gas. Water vapor sorption isotherms were S-shaped for both polymers, indicating the formation of water clusters. The water permeability decreased with vapor activity in both perfluoropolymers as the formation of these clusters decreased water diffusivity. The presence of the water clusters, however, had no impact on the performance of Cytop® and poly(50%PBVE-co-50%PDD) for CO2/CH4 separation. Typical concave sorption isotherms were obtained for toluene and xylene in poly(50%PBVE-co-50%PDD), while convex isotherms were observed in Cytop®. It was speculated that this change in isotherm shape may have been due to the small number of larger free volume elements within Cytop®, as observed in x-ray diffraction analysis. Neither toluene nor xylene had a significant impact on CO2 and CH4 permeabilities in Cytop®, while a gradual decrease in both permeabilities was noted for poly(50%PBVE-co-50%PDD) as the vapor activity increased, due to either competitive sorption or pore blocking. Finally, liquid glycol carryover caused no change on the performance of Cytop® membranes, while a slight drop in the CO2/CH4 separation factor for poly(50%PBVE-co-50%PDD) was observed.