Intracellular and extracellular sources, transformation process and resource recovery value of proteins extracted from wastewater treatment sludge via alkaline thermal hydrolysis and enzymatic hydrolysis

Yan, Yixin; Gao, Jianlei; Qin, Lei; Liu, Fan; Zeng, Wei; Wan, Junfeng

doi:10.1016/j.scitotenv.2022.158512

Cited by 16 publications

(5 citation statements)

References 56 publications

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“…For instance, the highest protein extraction efficiency in recalcitrant microalgae Scenedesmus sp. using NaOH-aided thermolysis was reported at 80°C for 90 min, while in more fragile microalgae like Synechococcus sp., the best protein yield was reported within 5 to 15 min at 90°C, and in activated sludge, optimal protein extraction is obtained at 100–140°C within 1.5–4 h ( Rausch, 1981 ; Yan et al, 2022 ). Comparing the chemical-assisted treatment groups, the NaOH-assisted treatment resulted in the highest protein yields both with 1 h (36.4 ± 0.7%) and 1 min (24.5 ± 0.2%) biomass-chemical reaction time, followed by the EDTA-assisted treatment.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of cell disruption methods for protein and coenzyme Q10 quantification in purple non-sulfur bacteria

Wada,

Rashid,

Wijten

et al. 2024

Front. Microbiol.

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A recent focus has been on the recovery of single-cell protein and other nutritionally valuable bioproducts, such as Coenzyme Q10 (CoQ10) from purple non-sulfur bacteria (PNSB) biomass following wastewater treatment. However, due to PNSB’s peculiar cell envelope (e.g., increased membrane cross-section for energy transduction) and relatively smaller cell size compared to well-studied microbial protein sources like yeast and microalgae, the effectiveness of common cell disruption methods for protein quantification from PNSB may differ. Thus, this study examines the efficiency of selected chemical (NaOH and EDTA), mechanical (homogenization and bead milling), physical (thermal and bath/probe sonication), and combined chemical–mechanical/physical treatment techniques on the PNSB cell lysis. PNSB biomass was recovered from the treatment of gas-to-liquid process water. Biomass protein and CoQ10 contents were quantified based on extraction efficiency. Considering single-treatment techniques, bead milling resulted in the best protein yields (p < 0.001), with the other techniques resulting in poor yields. However, the NaOH-assisted sonication (combined chemical/physical treatment technique) resulted in similar protein recovery (p = 1.00) with bead milling, with the former having a better amino acid profile. For example, close to 50% of the amino acids, such as sensitive ones like tryptophan, threonine, cystine, and methionine, were detected in higher concentrations in NaOH-assisted sonication (>10% relative difference) compared to bead-milling due to its less disruptive nature and improved solubility of amino acids in alkaline conditions. Overall, PNSB required more intensive protein extraction techniques than were reported to be effective on other single-cell organisms. NaOH was the preferred chemical for chemical-aided mechanical/physical extraction as EDTA was observed to interfere with the Lowry protein kit, resulting in significantly lower concentrations. However, EDTA was the preferred chemical agent for CoQ10 extraction and quantification. CoQ10 extraction efficiency was also suspected to be adversely influenced by pH and temperature.

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Section: Resultsmentioning

confidence: 99%

Evaluation of cell disruption methods for protein and coenzyme Q10 quantification in purple non-sulfur bacteria

Wada,

Rashid,

Wijten

et al. 2024

Front. Microbiol.

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“…The AA profile of zein agrees with the recent study [ 3 ]. The differences between AA profiles of zein and ZH 0.6–70 were due to the fact that only the sediments were collected; therefore, some free AAs generated during hydrolysis were removed from the final samples [ 44 , 45 ]. The total hydrophilic AA content was 32.63% vs. 35.54% for zein and ZH 0.6–70 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Functional Properties of Corn Byproduct-Based Emulsifier Prepared by Hydrothermal–Alkaline

et al. 2023

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As consumers’ interest in nature-sourced additives has increased, zein has been treated hydrothermally under alkaline conditions to prepare a nature-sourced emulsifier. The effects of mild hydrothermal–alkaline treatment with different temperatures or alkaline concentrations on the emulsifying properties of zein were investigated. The emulsification activity and stability index of zein hydrolysates increased by 39% and 164%, respectively. The optimal simple stabilized emulsion was uniform and stable against heat treatment up to 90 °C, sodium chloride up to 200 mmol/L, and pH values ranging from 6 to 9. Moreover, it presented excellent storage stability compared to commonly used food emulsifiers. The surface hydrophobicity caused the depolymerization of the tertiary structure of zein and the dissociation of subunits along with exposure of hydrophilic groups. The amino acid composition and circular dichroism results reveal that the treatment dissociated protein subunits and transformed α-helices into anti-parallel β-sheets and random coil. In conclusion, mild hydrothermal–alkaline treatment may well contribute to the extended functional properties of zein as a nature-sourced emulsifier.

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“…TH breaks down the sludge and releases a large amount of organic matter, mainly including proteins, polysaccharides, and lipids [39]. Among them, the hydrolysis of proteins increased the NH 4 + -N concentration in the solution [40]. Although the temperature was the same for TH and PTH, with the change in heating method from TH to PTH, more cell breakage occurred in EAS.…”

Section: Measurement Of Physicochemical Componentsmentioning

confidence: 99%

Preliminary Study on the Treatment Efficiency of Pasteurized Lime Thermal Alkaline Hydrolysis for Excess Activated Sludge and Reduction of Tetracycline Resistance Genes

Chen¹,

Zhou²,

Zhang³

et al. 2023

Journal of Renewable Materials

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Thermal alkaline hydrolysis is a common pretreatment method for the utilization of excess activated sludge (EAS). Owing to strict environment laws and need for better energy utilization, new methods were developed in this study to improve the efficiency of pretreatment method. Direct thermal hydrolysis (TH), pasteurized thermal hydrolysis (PTH), and alkaline pasteurized thermal hydrolysis (PTH + CaO and PTH + NaOH) methods were used to treat EAS. Each method was compared and analyzed in terms of dissolution in ammonium nitrogen (NH 4 + -N) and soluble COD (SCOD) in EAS. Furthermore, the removal of tetracycline resistance genes (TRGs)and class 1 transposon gene intI1 from EAS was investigated. The NH 4 + -N and SCOD concentrations in EAS treated by PTH were 1.24 and 2.58 times higher than those of TH. However, the removal efficiency of total TRGs and intI1 between the groups was comparable. The SCOD concentration of the PTH + NaOH group was 4.37 times higher than that of the PTH group, and the removal efficiency of total TRGs was increased by 9.52% compared with that by PTH. The NH 4 + -N and SCOD concentrations of the PTH + CaO group could reach 85.04% and 92.14% of the PTH + NaOH group, but the removal efficiency of total TRGs by PTH + CaO was 19.78% lower than that by PTH + NaOH. Thus, to reduce the financial cost in actual operation, lime (CaO) can be used instead of a strong alkali (NaOH), and pasteurized steam at 70°C instead of conventional high-temperature heating to treat EAS. This study provides a reference for the development of alkaline hydrolysis under moderate temperatures along with the removal of TRGs in EAS.

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Intracellular and extracellular sources, transformation process and resource recovery value of proteins extracted from wastewater treatment sludge via alkaline thermal hydrolysis and enzymatic hydrolysis

Cited by 16 publications

References 56 publications

Evaluation of cell disruption methods for protein and coenzyme Q10 quantification in purple non-sulfur bacteria

Evaluation of cell disruption methods for protein and coenzyme Q10 quantification in purple non-sulfur bacteria

Functional Properties of Corn Byproduct-Based Emulsifier Prepared by Hydrothermal–Alkaline

Preliminary Study on the Treatment Efficiency of Pasteurized Lime Thermal Alkaline Hydrolysis for Excess Activated Sludge and Reduction of Tetracycline Resistance Genes

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