Pretreatment Hydrolysis Research Articles

Diversity and fate of human pathogenic bacteria, fungi, protozoa, and viruses in full-scale sludge treatment plants

Sewage sludge, as the by-product of urban sewage biological treatment, is a potential reservoir and source of pathogens. However, the distribution and fate of different pathogens during sludge treatment and disposal remain unclear. Here, we investigated the diversity and fate of human pathogenic bacteria, fungi, protozoa, and viruses in sludge from four full-scale sludge treatment plants (STPs) using high-throughput sequencing approaches. The results indicated that the diversity of pathogens in different STPs was different, which may be related to sludge characteristics and local epidemics. Sludge treatment steps differentially affected pathogens reduction, and anaerobic digestion (AD) reduced the relative abundance and richness of pathogens. AD combined with thermal hydrolysis pretreatment effectively reduced most pathogenic bacteria except for Clostridium perfringens. Sanitary performance of AD was also varied by substrate characteristics (high-solid or low-solid sludge) and compositions (mono-digestion or co-digestion). Resistance of pathogens to sludge treatment was type-dependent, and pathogenic protozoa and fungi showed greater resistance to AD. Meanwhile, some pathogenic bacteria and viruses (Adenovirus and Herpesvirus) were widespread in digestate, revealing a biological risk in disseminating pathogenicity. These findings reveal the diversity and fate of human pathogens during sludge treatment and disposal, which would be crucial in monitoring and controlling pathogen proliferation.

Agrowastes of banana peels as an eco-friendly feedstock for the production of biofuels using immobilized yeast cells

Liquid biofuels such as bioethanol is a promising renewable fuel as it can be produced from various biomass wastes as feedstocks. The concept of waste to wealth approach is inevitable for bioethanol production. In Malaysia, banana peels are one of the largest agricultural wastes found in the local market. Thus, in this study, banana peels were used as a feedstock to produce bioethanol through fermentation using immobilized yeast cells. For higher yield of bioethanol, optimization parameters were conducted for both dilute acid hydrolysis and fermentation process. First, the banana peels were sliced and oven-dried at 70°C for 24 h before being ground to fine powder. Then, the samples were subjected to dilute acid hydrolysis. Parameters such as concentration of H2SO4, temperature and time were optimized during the hydrolysis. Higher amount of reducing sugar was obtained at 0.10 M H2SO4, at 90°C for 20 min with 5.190 mg/mL, 5.196 mg/mL and 5.306 mg/mL respectively for the hydrolysis process. Yeast Saccharomyces cerevisiae was immobilized using 3% (w/v) of sodium alginate and 2% (w/v) calcium chloride using entrapment technique, in the form of beads. These immobilized beads were added into the fermentation medium together with the optimized pretreated hydrolysate of banana peels. Parameters such as cells loading (weight of beads), pH, temperature and time were also optimized in the fermentation process. From the results, it was found out that the optimized parameters of 9g of cells loading, pH 5, at 30°C for 24 h utilized more sugar during fermentation process based on the absorbance reading.

Different Preparation Method of Nanocellulose from Macaranga gigantea and Its Preliminary Study on Packaging Film Potential

Nanocellulose is a versatile cellulosic nanomaterial that can be used in many application areas. Applying different preparation strategies leads to different types of nanocellulose. In this study, nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC) were prepared from lesser known wood species, viz., Macaranga gigantea, using sulfuric acid hydrolysis and enzymatic pretreatment with ultrafine grinding approaches, respectively. The respective nanocellulose was characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), atomic force microscopy (AFM). It was then converted into a thin film to assess its performance which includes tensile test, transparency, air permeance, water vapor transmission rate (WVTR), and water vapor permeability (WVP) properties. NCC and NFC produced from the raw material of Macaranga had average widths of 6.38 ± 3.92 nm and 13.17 ± 12.71 nm, respectively. Peaks in FTIR spectra showed the conversion of Macaranga wood to nanocellulose by the presence of cellulose fingerprint as well as absence of lignin and hemicellulose after alkaline treatment. The successful conversion was also supported by XRD analysis which displayed the increased crystallinity value from 54% to 70%. TGA decomposition pattern at 200-490 °C revealed the thermal stability of the samples. The thin film produced from nanocelluloses had WVTR values of 4.58 and 12.14 g/(day·m2) for NFC and NCC, respectively, comparable to those of films from polyester and oriented polypropylene. Nanocellulose-based thin film has the potential to be used as sustainable and biodegradable packaging.

Improvement of gaseous bioenergy production from spent coffee grounds Co-digestion with pulp wastewater by physical/chemical pretreatments

Two steps of hydrolysis and anaerobic biogas production processes was investigated in this study. In the first step, subcritical water (SBW) hydrolysis and chemical (acid/alkali) pretreatments were carried out to enhance hydrolysis efficiency by obtaining and analyzing the total volatile fatty acids (TVFA), chemical oxygen demand (COD), and total sugar productions from spent coffee grounds (SCG) hydrolysate. The subcritical water (SBW) hydrolysis under the condition of temperature 150 °C for 30 min can greatly improve the organic matter breakdown and reached the COD concentration of 1010 g/L which was 30% higher than the untreated raw SCG. For chemical pretreatments, it was found that the alkaline hydrolysis of SCG resulted in the greatest total sugar concentration of 181 g/L whereas the operation conditions were 2.0 M NaOH at 60 °C for 1 h. The peak of TVFA concentration 3725 mg/L was found at the acid hydrolysis of SCG with 1.0 M H2SO4 acid, 60 °C for 1 h. The optimal biomethane yield of 115 mL/g COD was obtained when 1.0 M H2SO4 acid hydrolysate co-digestion with pulp wastewater which increase methane yield production 8 times of raw pulp wastewater. The pretreatment process was confirmed in this study can significant improve the converting of the biowastes to bioenergy efficiency.

Performance and methane potential of up-flow anaerobic sludge blanket treating thermal hydrolyzed sludge dewatering liquor

Thermal hydrolysis pretreatment could release organic sufficiently from solid into liquid phase to accelerate the high solid sludge anaerobic digestion. Thus, up-flow anaerobic sludge blanket (UASB) could be a promising energy recovery process to treat thermal hydrolyzed sludge dewatering liquor with significantly augmented the organic loading rate (OLR). In this study, its performance was investigated using a lab-scale UASB to treat sludge dewatering liquor after 165 °C, 30 min thermal hydrolysis pretreatment. The results show that 85.57% of the organic in thermal hydrolyzed sludge dewatering liquor could be converted to methane. The UASB adapts to high OLR stably, and the COD removal efficiency was 71.98 ± 1.95% at OLR of 18.35 ± 0.78 kgCOD·(m3·d)-1, and the gap between the maximum potential and experimental methane production yields could be observed during different OLRs. It could be explained as the methanogenesis rate decreased due to the shift of dominant pathway from acetoclastic methanogenesis to syntrophic acetate oxidation following hydrogenotrophic methanogenesis. Methanospirillum became the dominant methanogen with the increase of OLR. In addition, the methane production yield and rate would be hindered till the ammonia nitrogen concentration exceeds 4 g·L-1. Direct interspecies electron transfer could be promising methods to improve UASB performance treating thermal hydrolyzed dewatering liquor.

Valorization of Pineapple Leaves Waste for the Production of Bioethanol.

Being a lignocellulose-rich biomass, pineapple leaves waste (PL) could be a potential raw material for the production of biofuel, biochemicals, and other value-added products. The main aim of this study was to investigate the potential of pineapple leaves in the sustainable production of bioethanol via stepwise saccharification and fermentation. For this purpose, PL was subjected to hydrothermal pretreatment in a high-pressure reactor at 150 °C for 20 min without any catalyst, resulting in a maximum reducing sugar yield of 38.1 g/L in the liquid fraction after solid-liquid separation of the pretreated hydrolysate. Inhibitors (phenolics, furans) and oligomers production were also monitored during the pretreatment in the liquid fraction of pretreated PL. Enzymatic hydrolysis (EH) of both pretreated biomass slurry and cellulose-rich solid fraction maintained at a solid loading (dry basis) of 5% wt. was performed at 50 °C and 150 rpm using commercial cellulase at an enzyme dose of 10 FPU/gds. EH resulted in a glucose yield of 13.7 and 18.4 g/L from pretreated slurry and solid fractions, respectively. Fermentation of the sugar syrup obtained by EH of pretreated slurry and the solid fraction was performed at 30 °C for 72 h using Saccharomyces cerevisiae WLP300, resulting in significant ethanol production with more than 91% fermentation efficiency. This study reveals the potential of pineapple leaves waste for biorefinery application, and the role of inhibitors in the overall efficiency of the process when using whole biomass slurry as a substrate.

The neglected effects of polysaccharide transformation on sludge humification during anaerobic digestion with thermal hydrolysis pretreatment

Humus accumulation during sludge stabilization is attracting increasing attention because of its land use potential. This study investigated the effects of thermal hydrolysis pretreatment (THP) on sludge humification and the related regulatory mechanisms during anaerobic digestion (AD). The sludge subjected to AD with THP at 160 °C (AnD-160) exhibited 7.3% and 8.5% higher total extractable carbon (TEC) and humic acid carbon (HAC) concentrations than the unpretreated sludge, respectively, while the sludge subjected to AD with THP at 180 °C (AnD-180) exhibited 1.4% and 7.0% lower concentrations. Humification of AnD-160 and AnD-180 were enhanced and inhibited, respectively. THP influenced sludge humification during AD through both intracellular polyphenol synthesis and extracellular humus condensation pathways related to polysaccharide metabolism. The 160 °C-pretreated sludge exhibited higher polysaccharide availability (more soluble polysaccharides and reducing sugars) than the other samples and thus had more active intracellular polyphenol metabolism during AD. The polyphenol accumulation stimulated the synthesis of related condensation enzymes (polyphenol oxidase and quinone oxidoreductases), facilitating extracellular HA production during AD. However, THP at 180 °C resulted in the highest production of melanoidins with CO-C heterocycles through C = O and CH sites of polysaccharides (778.46 vs. 193.87 R.U. nm2-mL/g for the unpretreated sample). This heterocyclization decreased the polysaccharide availability and inhibited intracellular polyphenol synthesis, consequently inhibiting condensation enzymes supply and extracellular HA production during AD. Overall, this study highlights the crucial but neglected role of polysaccharides in sludge humification during AD: the availability of polysaccharides affected by their occurrence state and molecular structure could determine the humification, which can be regulated by THP at different temperature.

Unblocking the rate-limiting step of the municipal sludge anaerobic digestion.

Anaerobic digestion stabilizes municipal sludge through total solids reduction and biogas production. It is generally accepted that hydrolysis accounts for the rate-limiting step of municipal sludge anaerobic digestion, impacting the overall rates of solids reduction and methane production. Technically, the sludge hydrolysis rate can be enhanced by the application of thermal hydrolysis pretreatment (THP) and is also affected by the total solids concentration, temperature, and solids retention time used in the anaerobic digestion. This study systematically analyzed and compared ways to take these four factors into the consideration of modern anaerobic digestion system for achieving the maximum solid reduction. Results showed that thermophilic anaerobic digestion was superior to mesophilic anaerobic digestion in terms of solids reduction but vice versa in terms of the methane production when integrated with THP. This difference has to do with the intermediate product accumulation and inhibition when hydrolysis outpaced methanogenesis in THP-enhanced thermophilic anaerobic digestion, which can be mitigated by adjusting the solids retention time. PRACTITIONER POINTS: THP followed by TAD offers the greatest solids reduction rate. THP followed by MAD offered the greatest methane production rate. FAN inhibition appears to be an ultimate limiting factor constraining the methane production rate. In situ ammonia removal technique should be developed to further unblock the rate-limiting step.

Fate of antibiotic resistance genes and class 1 integrons during sludge treatment using pilot-scale anaerobic digestion with thermal hydrolysis pretreatment

This work evaluated the fate of antibiotic resistance genes (ARGs) and class 1 integron gene in sewage sludge before and after pilot-scale thermal hydrolysis pretreatment (THP) and subsequent mesophilic anaerobic digestion (AD) treatment. Variables investigated include THP temperatures, feedstock types, and AD solids retention times. Real-time polymerase chain reaction was performed to quantify the ARGs in feedstocks, THP and AD effluent. Results show that THP significantly (t test, p < 0.05) reduced the absolute abundances of most ARGs, with the reduction ranging from 0.03 to 3.09 log units. Rebound effects of ARGs in the subsequent AD were observed and were relevant with tested variables; shorter solids retention time (10 days) and higher THP temperature (165 ℃) can significantly reduce ARGs in AD effluent. These findings provide references about the effects of the THP and AD on the control of ARG spread from sewage sludge to environments.

An integrated process using acetic acid hydrolysis and deep eutectic solvent pretreatment for xylooligosaccharides and monosaccharides production from wheat bran

Organic acid hydrolysis for xylooligosaccharides (XOS) production from lignocelluloses provides the benefits of simple operation, rapid reaction and high XOS yield. However, no literature reported the XOS production from wheat bran (WB) by organic acid hydrolysis. In this paper, acetic acid (AA) hydrolysis was employed to produce XOS from WB. After AA hydrolysis (5 %, v/v, 170 °C, 20 min) of 100 g/L WB, the concentrations of X2, X3, X4, X5 and X6 were 2.4, 5.0, 1.9, 1.9 and 1.4 g/L respectively and the total XOS yield was 62.9 %, which was the highest among the previous researches. The arabinose yield reached 76.1 %. Then, AA-hydrolyzed WB was delignified by deep eutectic solvent (DES) pretreatment and the resulting residue had the glucose and xylose yields of 83.8 % and 54.8 %, respectively. This work offers a productive method for the conversion of WB into XOS, arabinose and glucose by AA hydrolysis and DES pretreatment.

Effect of single and combined pretreatment strategies applied to Chlorella vulgaris biomass on bioethanol production

Microalgae serve as an attractive feedstock for the production of third-generation bioethanol because of their rich carbohydrates. The conversion of biomass to ethanol necessitates a saccharification step in which complex carbohydrates are hydrolyzed into sugars that can be fermented to bioethanol. The recalcitrance of microalgal cell envelopes, which are difficult to depolymerize and render internal carbohydrate reserves inaccessible to hydrolysis, impedes carbohydrate mobilization. Saccharification occurs through acidic or alkaline hydrolysis, enzyme hydrolysis, or a combination of the three methods. Mobilization of carbohydrates in large amounts requires expensive pretreatment techniques. The goal of this study was to produce bioethanol via chemo-enzymatic pretreatment of Chlorella vulgaris biomass using single and combined pretreatment strategies. The single pretreatments were acid, alkaline, and enzymatic hydrolysis, and combined pretreatment strategies were acid and enzyme hydrolysis; alkaline and enzyme hydrolysis; acid, alkaline and enzyme hydrolysis. For single pretreatment strategies, the highest reducing sugar yields were; 1.70 g mL−1 at 1.2 mol L−1 of NaOH carried out at 120 °C for 30 min, 1.42 g mL−1 at 0.2 mol L−1 of H2SO4 carried out at 121 °C for 30 min and 1.31 g mL−1 with 1.0 × 107 spores/mL of A. niger incubated at room temperature (28°C ± 2) for 7 days. For the combined pretreatment strategies, NaOH and enzyme hydrolysis produced the highest reducing sugar yield of 1.90 g mL−1. The highest bioethanol yield of 5% w/v was obtained with the NaOH and enzyme hydrolysis pretreatment strategy. Further studies to understand the effect of various factors during the pretreatment and fermentation stages will help optimize and improve the bioethanol yield from microalgal feedstock.

Accelerated stabilization of high solid sludge by thermal hydrolysis pretreatment in autothermal thermophilic aerobic digestion (ATAD) process.

Autothermal thermophilic aerobic digestion (ATAD) is a rapid biological treatment technology for sludge stabilization. To improve digestion efficiency and shorten stabilization time, thermal hydrolysis pretreatment was employed before ATAD of high solid sludge. The results showed that accelerated stabilization of high solid sludge (total solid=10.1%) was achieved by thermal hydrolysis pretreatment with volatile solid removal efficiency of 40.3% after 8 days of ATAD, 11 days earlier than unpretreated sludge. The enhanced release and hydrolysis of intracellular organics resulted in a solubilization degree of 45.3%. The reduced sludge viscosity and improved fluidity after thermal hydrolysis facilitated mixing, aeration and organics degradation during ATAD. Excitation emission matrix analysis indicated that the fluorescence intensity of soluble microbial byproduct and tyrosine-like protein increased markedly after thermal hydrolysis and decreased after ATAD. The proportion of high molecular weight (MW>10kDa) substances in the supernatant increased significantly after thermal hydrolysis, while the low MW (MW<1kDa) substances decreased after ATAD. The significant difference in microbial composition between the pretreatment and control groups elucidated the accelerated sludge stabilization under thermal hydrolysis. This work provides an efficient and practical strategy to achieve rapid stabilization of high solid sludge.

Anaerobic co-digestion of sewage sludge pretreated by thermal hydrolysis and food waste: gas production, dewatering performance, and community structure

ABSTRACT Anaerobic co-digestion can effectively break the limitations of mono-digestion. However, there are still some problems such as long residence time, unsatisfactory methane yield, and unstable performance for co-digestion of sewage sludge (SS) and food waste (FW). Therefore, the SS in the reactor treating co-digestion of SS and FW is considered to be pretreated by thermal hydrolysis. In this work, the anaerobic co-digestion of SS of thermal hydrolysis pretreatment (THP) and FW significantly improved the stability, methane production of the digestive reactor, and dewaterability of the digested sludge. The R6 obtained the most cumulative methane production (315.76 mL/g VS). In addition, compared to R3, the cumulative methane production and maximum methane production rate of R5 increased by 9.93% and 14.56%, respectively. The dewaterability of R4, R5, and R6 was improved, while the dewatering performance of the R3 decreased to a greater extent. The results of the kinetic model fitting were consistent with the experimental results. Among them, the hydrolysis constants (Kh) of anaerobic co-digestion of THP-SS and FW were 0.121, 0.130, and 0.114 d−1, respectively, which were higher than those of other groups. And the estimated lag time (λ) of co-digestion was also lower than that of mono-digestion groups. Microbial community analysis indicated that the bacterial diversity and richness of anaerobic co-digested groups of THP-SS and FW were enhanced, while the methanogens with acetoclastic pathway became the main methanogenic microorganisms. This work provides essential information on anaerobic co-digestion containing different THP-SS contents.

Metagenomic analysis reveals the size effect of magnetite on anaerobic digestion of waste activated sludge after thermal hydrolysis pretreatment

Although magnetite has been widely investigated in anaerobic digestion (AD), its role in the practical AD of waste-activated sludge (WAS) after thermal hydrolysis pretreatment (THP) and its size effect remain unclear. In this study, magnetite with four different particle sizes was added during the AD of WAS after THP. With the reduction of magnetite particle size, cumulative methane production was increased, while the optimal dosage of magnetite decreased, with 0.1 μm magnetite at an optimal dosage of 2 g/L achieving the highest cumulative methane production increase of 111.97 % compared with the blank group (without magnetite). Smaller magnetite particles increased α-glucosidase and protease activities, coenzyme F420 concentration, and electron-transport system activity (20.30 %, 173.02 %, 60.39 % and 158.08 % higher respectively than the blank group). The size of magnetite also influenced the establishment of direct interspecies electron transfer (DIET) during AD. Based on the analysis of the pilA gene abundance, magnetite with a large particle size could promote the formation of e-pili in syntrophic electroactive bacteria (Clostridium, Syntrophomonas, and Pseudomonas) and methanogens (Methanospirillum), thereby completing electron transfer. However, small-sized magnetite particles stimulated DIET by enhancing the secretion of conductive proteins in extracellular polymeric substances and membrane-bound enzymes (Fpo) in Methanosarcina.

Influence of thermal hydrolysis on sludge anaerobic digestion: Release of humic acid promotes electron transport of methanogen

Thermal hydrolysis pretreatment (THP) has been widely applied to promote anaerobic digestion (AD). Humic acids (HAs) are a group of insoluble organics and often present in the conventional AD of sludge, but are reportedly substantially released during THP. Thus, the influences of the released HAs on AD shall be investigated, in particular on methanogenesis. Our results indicated that the presence of HAs extracted from thermally hydrolyzed sludge improved methanogenesis by 15.8–80.8%. However, HAs harvested at different temperatures presented distinctively different capabilities in enhancing methane production. Seemingly, the promotion efficiency of HAs to methanogenesis did not significantly respond with any individual characteristics of HAs in aspects of molecular weight, electrical activity and electroactive group compositions. However, the efficiency presented an evident correlation with the superimposed effects of the characteristics aforementioned. Therefore, a hypothesis on the mechanism involved in the phenomenon observed above was proposed that only the HAs with low molecular weight, allowing the molecules to penetrate cells could affect methanogenesis, and not all of the electroactive groups of HAs were involved in microbial electron transfer. Moreover, it was found that only the group of quinones (Q1) with side chain of electron withdrawing group played key roles in accelerating methyl acetyl-CoA degradation and promoting methanogenesis. Directional regulation of methanogenesis promotion assisted with HAs was realized by selectively removing or retaining the Q1 groups in HAs, which also evidently sustained the proposed mechanism aforementioned. The findings of this study demonstrate that high temperature was conducive to the release of organics during sludge thermal hydrolysis, whereas the temperature above 160℃ led to changes of HAs structure and then subsequently undermined methane production from sludge.

Optimisation of pre-harvest sago frond sap for the production of l-lactic acid using Lactococcus lactis IO-1

The major restriction of sago palm plantation is the long maturation period for the starch extraction. As such, alternative commodity has to be identified to increase commercial value of sago palm especially from the by-product. Sago frond has been harvested to have numerous advantages as an alternative substrate for the production of biomaterial and biofuel such as lactic acid and bioethanol. This study focuses on effective approach to maximise the concentration of sugar in the substrate and to identify the ideal concentration of sago frond sap (SFSp) as sole media to produce l-lactic acid and grow L. lactis IO-1. Result shows that SFSp extracted from sago rachis using a roller press machine contained glucose (43.8 g/L), xylose (17.3 g/L) as free sugars and starch (5.55 g/L). Combination of enzymatic hydrolysis and sterilisation pre-treatment was found to maximise the concentration of total carbon source (68 g/L) and sterilised sago frond sap suitable to be used for fermentation process. The ideal concentration of SFSp that was determined at 50% dilution produces the highest amount of l-lactic acid (24.02 g/L) synergist by most efficient sugar consumption (89.93%). The use of SFSp as fermentation medium for l-lactic acid production generated maximum biomass concentration of 14.53 g/L. The utilisation of SFSp extracted from pre-harvest sago frond as substrate promote efficiency of l-lactic acid production associated to exceptional growth performance of L. lactis IO-1. In conclusion, the concept of utilizing by-product from sago palm as novel raw material promise reliable resources and superiority of L. lactis IO-1 to metabolise sugar in SFSp promote lucrative and ethical production of l-lactic acid.

Hidrólisis ácida de hemicelulosa de Ipomoea arborecens: Cinética de producción de xilosa

In this paper the composition change of Ipomoea arborescens was evaluated under acid hydrolysis pretreatment, and the kinetic parameters of this reaction were determined. The goal was to evaluate the effects of particle size in the reaction rate of hemicellulose hydrolysis, and to find the concentration of sulfuric acid in which the reaction mechanism favors hemicellulose hydrolysis of Ipomoea arborescens particles. Once the best conditions were found, Ipomoea arborescens particles were hydrolyzed at different temperatures. A pseudo-homogenous model was adopted to describe hemicellulose hydrolysis. The empirical formula of hemicellulose was determined experimentally to have 21 molecules of xylose, 5 molecules of glucose and 1 molecule of galactose. The mathematical model of hemicellulose hydrolysis is successful to describe the experimental results when the temperature is between 120 and 160°C.

Insight into magnetite effects on anaerobic digestion of waste activated sludge with thermal hydrolysis pretreatment: From reactor performance to metagenomics analysis

Although the promotion of magnetite in anaerobic (AD) has been widely reported, the role of magnetite plays in the AD of waste activated sludge (WAS) and the mechanism of the promotion effect are still needed to be explored. This study investigated the effects of magnetite in AD of WAS with thermal hydrolysis pretreatment (THP) from four aspects including reactor performances, sludge characteristics, microbial community structures and gene abundance. Results showed that magnetite is able to enhance the consumption of soluble protein (SPN) and soluble polysaccharide (SPS) by increasing the activities of α-glucosidase and protease. With the addition of 0.5–5 g/L magnetite, the cumulative CH4 production could be increased by 38.25 %–85.34 %. The sludge electrical conductivity (EC) grew with the increase of magnetite dosage, which were 3.02, 8.65, 13.00, 15.46 and 17.97 μS/cm for G0-G4 respectively. In the presence of magnetite, the abundance of Proteobacteria increased which contained many genera of electroactive bacteria, such as Pseudomonas. By further metagenomics analysis, hydrogenotrophic methanogenesis pathway was shown to be enhanced with the addition of magnetite. The increasing abundance of pilA genes from Clostridium and Pseudomonas in bacteria and Methanospirillum in archaea confirmed that magnetite stimulated DIET in the AD of WAS.

The Effect of Hydrolysis Pre-Treatment by Flavourzyme on Meat Quality, Antioxidative Profiles, and Taste-Related Compounds in Samgyetang Breast Supplemented with Black Garlic.

This study aimed to carefully investigate the effect of hydrolysis using Flavourzyme on meat quality, antioxidative status, and taste-related compounds in breast of Samgyetang that was supplemented with black garlic (BG). Four different treatment groups were compared: (1) conventional Samgyetang (control), (2) Samgyetang hydrolyzed with Flavourzyme (1%, v/w) (FS), (3) Samgyetang made with the BG extract without hydrolysis (NBG), and (4) BG samgyetang pre-treated with Flavourzyme (1%, v/w) in a water bath at 55°C for 2.5 h and hydrolyzed before being processed (HBG). All the treatment groups were cooked by retorting at conditions 121°C and 1.5 kg/cm2 for 1 h. Improved umami profiles through the increase of umami-related nucleotides (5’-GMP, 5’-IMP) and free amino acids—aspartic acid and glumtamic acid, in Samgyetang breast was recorded following hydrolysis. The HBG group tended to impart stronger scavenging activity toward free radicals compared with the other two groups, while not differing with NBG group regarding suppressing malondialdehyde. Textural properties were improved through hydrolysis, wherein the shear force value decreased from 2.29 kgf in the control to 1.19 and 1.25 kgf in the FS and HBG group. Moisture percentages were highly retained, with the redness score increasing and the lightness color decreasing following hydrolysis. In conclusion, the results of this study can be a preliminary information of the effect of hydrolysis pre-treatment for BG samgyetang. Further experiments are required to compare various enzymes along with its organoleptic acceptances.

Combined thermal hydrolysis pretreatment and anaerobic co-digestion of waste activated sludge and food waste

In this study, the impact of thermal hydrolysis pretreatment (THP) on the mono- and co-digestion of thickened waste activated sludge (TWAS) and food waste (FW) was carried out at temperatures of 150, 170, 190, and 210 °C and volumetric ratios of 90:10, 70:30, and 50:50 in batch anaerobic tests. THP enhanced solubilization, reduced volatile suspended solids (VSS) and the particle size of TWAS as the temperature increased showing optimal improvements at 170 °C. THP showed no significant impact on FW with only marginal improvements at 150 °C. Increasing the temperature beyond 170 °C for TWAS and 150 °C for FW deteriorated anaerobic biodegradability forming refractory compounds. Co-digestion improved methane yields and kinetics as the contribution of FW increased. Co-digestion of thermally pretreated TWAS with FW improved the methane yields by 27% and kinetics by 29% at 170 °C with no synergism. Co-digestion of thermally pretreated FW with TWAS improved methane yields by 15% and kinetics by 25% at 150 °C, with improvements up to 21% in synergy. THP of the mixed feedstocks improved methane yields by 53% and kinetics by 92% at 170 °C, with improvements becoming less pronounced with the increase in the volume of FW and temperature.