Hydrolysable Amino Acids Research Articles

Engineering a Carboxypeptidase from Aspergillus Oryzae M30011 to Improve the Terminal Specific Enzymatic Hydrolysis of Aromatic Amino Acids

Engineering a Carboxypeptidase from Aspergillus Oryzae M30011 to Improve the Terminal Specific Enzymatic Hydrolysis of Aromatic Amino Acids

Estimates of protein in coastal marsh soils: A case study of the utility of the Bradford assay for quantifying soil protein

The fraction of soil protein extracted by autoclaving soil (AESP) has emerged as a potential indicator of available organic nitrogen (N), aggregate stability, and soil carbon (C) storage potential. Estimates of AESP are often based on colorimetric assays—primarily the Bradford assay—yet the results of these assays can be confounded by interference from polyphenolic contaminants of soil protein extracts. The extent to which polyphenolic interference in the Bradford assay may contribute to over- or underestimation of AESP content and whether a correction can be made for the interference has remained unclear. Here, we present a case study of how Bradford-based estimates of AESP compared to maximum and minimum estimates of AESP across two chronosequences of marsh soils that ranged widely in soil organic matter concentration (20–580 mg·g−1). Our maximum estimates were based on the amount of N in the dialyzed extracts; our minimum estimates were based on the proportion of the extracted N that was accounted for by hydrolysable amino acids. We observed that the Bradford-based estimates usually followed trends that were qualitatively similar to those of the maximum and minimum estimates across different marshes. However, the Bradford-based estimates were almost always greater than the maxima (by up to 450%) and never below the minima. This extent of overestimation was positively correlated with the C:N ratio of the extracts, but the relationships between the overestimates and C:N ratios differed between the two chronosequences. Contrary to what has been previously suggested, the dilution of extracts only exacerbated the extent of overestimation in the Bradford assay. Instead of a continued reliance on the Bradford assay for AESP measurements, we propose that the N content of semi-purified soil extracts serve as a surrogate metric for AESP, primarily because it may be more amenable to inter-study comparisons while still being feasible for most soil laboratories.

Nutritional evaluation of fish protein hydrolysate and its application in piglet production.

This study was conducted to determine the digestible energy (DE), metabolizable energy (ME), and ileal digestibility of amino acids (AA) of fish protein hydrolysate (FPH), and to evaluate the effects of FPH on the performance of piglets. In Exp. 1, the available energy content of FPH was determined by difference methods: 12 barrows with an initial body weight (BW) of 40.0±2.1kg were randomly assigned into two dietary treatments with six replicates per treatment, the treatments contained a corn basal diet and an experimental diet in which 20% corn was replaced by FPH. The experiment lasted for 12 d, with 7 d adaptation period followed by 5 d total collection of feces and urine. In Exp. 2, the standardized ileal digestibility (SID) of AA in FPH by the N-free method was determined, 12 barrows (initial BW of 35.3±1.8kg) with ileal T-cannulas were randomly allotted into two treatments with six replicates per treatment, and the dietary treatments consisted of an experimental diet and a N-free diet. The experiment was lasted for 7 d, with 5 d adaptation period followed by 2 d collection of ileal digesta. In Exp. 3, the effect of FPH on the performance of piglets was conducted. One hundred ninety-two piglets (initial BW of 8.10±1.8kg) were randomly allotted into four treatments with six replicates per treatment. The treatments were a control diet with fish meal (FM) and part or all FM was replaced by FPH, receiving diets containing 2%, 3%, or 5% FPH. The experiment lasted for 28 d. Results showed that in Exp. 1, the DE and ME of FPH were 21.12 and 20.28 MJ/kg. In Exp. 2, the SID of Lys, Met, Thr, and Trp was 79.99%, 87.17%, 68.29%, and 71.53%, respectively. In Exp. 3, addition of 3% FPH increased nutrient digestibility and volatile fatty acid content in feces. Addition of 5% FPH increased the average daily feed intake (ADFI), significantly increased (P < 0.05) the activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and immunoglobulin A (IgA), while significantly decreased (P<0.05) the average daily gain (ADG). In conclusion, FPH had a high value of digestible energy and ileal digestible essential amino acids, and could improve nutrient digestibility, immunity, antioxidant capacity, and intestinal health of piglets, while adverse to nitrogen deposition in piglets.

Abiotic Aggregation of Organic Matter in Coastal and Estuarine Waters: Cases in the Eastern Long Island Sound, USA

Organic aggregates, which formed from small particles and dissolved material, were chemically characterized in the Long Island Sound coastal waters. In this study, six aggregation experiments were conducted on low-salinity samples (the Thames River, CT, USA; salinity of 6.3–6.8) and high-salinity samples (the coast of Avery Point, CT, USA; salinity of 21.4–26.7). Water samples were incubated on a roller table for two days under dark conditions to generate laboratory-made aggregates. Particulate organic carbon (POC) concentrations increased 5–39% after two days of rolling. A higher POC increase occurred in low-salinity samples. The concentrations of neutral aldoses and amino acids, as well as their C- and N-yields, decreased during the experiments (except for particulate hydrolysable amino acid in low-salinity samples), while bacterial abundance increased 50–476%, indicating microbial degradation of biologically labile organic matter. Particulate hydrolysable amino acid was preferentially preserved in P-limited systems. An enrichment factor analysis showed the preferential microbial degradation of particulate hydrolysable neutral aldose and glucose appeared as the most labile aldose. The increase in bulk POC and the decrease in the fraction of labile organic carbon (neutral aldose and amino acid) in the particulate phase resulted in an accumulation of uncharacterized (presumably more refractory) particulate organic matter.

Engineered asparaginase from Erwinia chrysanthemi enhances asparagine hydrolase activity and diminishes enzyme immunoreactivity ‐ a new promise to treat acute lymphoblastic leukemia

AbstractBACKGROUNDThe treatment of acute lymphoblastic leukemia (ALL) uses the biopharmaceutical l‐asparaginase (ASNase) as the main medication. This drug, from bacterial origin (Escherichia coli or Erwinia chrysanthemi), depletes l‐asparagine (Asn) and secondarily l‐glutamine (Gln – GLNase activity) from the bloodstream, leading leukemic cells to die by deprivation of Asn. The use of ASNase is limited by the high incidence of adverse effects, which collectively can specifically impair quality of life of patients. Its high toxicity caused by the product of the hydrolysis of amino acids and the formation of anti‐ASNase antibodies often required treatment interruption, thus reducing the chances of cure and increasing the rates of disease relapse.RESULTSIn order to improve enzymatic activity, while reducing toxicity, we developed through directed evolution a double‐mutant ASNase from Erwinia chrysanthemi (Erw_DM), which has specific activity for Asn 46% higher than the wild‐type enzyme (Erw_WT). This makes it possible to reduce the amount of protein necessary for depletion of this amino acid and, consequently, the reduction of GLNase activity, considered toxic. In silico analysis showed that a lower number of epitopes was exposed, resulting in reduced recognition of the recombinant protein by antibody anti‐ASNase observed in vitro assay. Furthermore, we observed the same cytotoxic profile for the MOLT‐4 and REH ALL cell lines using 40% lower protein mass of Erw_DM to achieve the minimum enzyme activity required in the bloodstream during treatment.CONCLUSIONAltogether, our findings describe a potent and less immunogenic ASNase, an improvement that may alleviate treatment adverse effects developed in anti‐ALL therapy. © 2021 Society of Chemical Industry (SCI).

Effect of co-inoculation and sequential inoculation of Lactobacillus fermentum and Pichia kluyveri on pork hydrolysates fermentation

This is the first study on exploiting a LAB - Lactobacillus fermentum PCC and a yeast Pichia kluyveri (FrootZen) as starter cultures in meat-based sauce fermentation. An apparent antagonistic relationship was observed between these two cultures. P. kluyveri proliferated with an increased cell count of only 1.14 log CFU/mL and dropped to the original level (approx. 5.8 log CFU/mL), while the LAB growth was stimulated by increasing the cell count by 1.67 log CFU/mL in simultaneous inoculation. More pleasant fruity aromatic esters such as hexyl acetate and 2-phenylethyl acetate were detected in the sequential inoculation, while more acetic acid was detected in the simultaneous inoculation. However, there were no significant differences (P ≥ 0.05) in the glucose usage, production of organic acids, and amino acids in the fermented pork hydrolysates between these two inoculation methods.

Distribution and bioavailability of dissolved and particulate organic matter in different water masses of the Southern Yellow Sea and East China Sea

As the largest marginal seas, the Southern Yellow Sea (SYS) and the East China Sea (ECS) are important areas to study the biogeochemical cycles of organic matter from different sources. Seawater samples were collected from the SYS and ECS to determine the composition of organic carbon and major biochemicals (amino acids and carbohydrates) making up the dissolved (DOM) and particulate organic matter (POM). Concentrations of dissolved organic carbon (DOC) in the surface waters exhibited a latitudinal gradient, with high values appearing in the Yellow Sea Coastal Current Water (YSCCW). As the labile fraction of DOM, the concentrations of total hydrolysable amino acids (THAA) and total dissolved carbohydrates (TDCHO) were variable and tended to decrease from inshore to offshore sites. The DOC, THAA, and TDCHO concentrations were negatively correlated with salinity, suggesting that physical mixing and lateral transport played an important role in the distribution of DOM. In contrast, phytoplankton production directly affected the particulate amino acid (PAA) concentrations. High concentrations of PAA in the bottom water along a transect were probably due to resuspension by strong currents. DOC-normalized yields of THAA and TDCHO (THAA-C% and TDCHO-C%) were used to characterize the bioavailability of DOM in different water masses. Elevated THAA-C% values occurred in regions with high phytoplankton biomass, while high TDCHO-C% values were widespread in the Yellow Sea Warm Current Water (YSWCW) and the YSCCW. THAA-C% and TDCHO-C% had similar depth distributions, higher in the surface and middle layers than in the bottom layer, suggesting that organic matter undergoes diagenetic alterations as it sinks. The degradation index (DI) of DOM was lower than that of POM, which could be explained by their different sources and degradation states. The sporadic occurrence of hot spots likely represented important sites of biological activity. • Concentration, chemical composition, and bioavailability of OM were studied. • Physical mixing and lateral transport affect the distribution of DOM. • Amino acid and carbohydrate yields decreased with water depth. • Hot spots of bioavailable DOM occur sporadically in the surface water.

Variability in hydrolyzed amino acids contents in fresh leaves of Wuyi Rock Tea from different regions of China

Variability in hydrolyzed amino acids contents in fresh leaves of Wuyi Rock Tea from different regions of China

Production of nutty-like flavour from soybean protein isolate hydrolysate pretreated or assisted by microwave irradiation: impact of encapsulation on nutty flavour quality.

The aim of this study was to prepare a nutty-like flavour from enzymatic hydrolysates of soybean protein isolate pretreated or assisted by microwave heating. In both cases the time of microwave heating was optimized and degree of hydrolysis (DH) and content of free amino acids in each hydrolysate were determined and compared with those of hydrolysate prepared by conventional method (E-HSC). The hydrolysates showed the best results were used as main precursors of nutty flavour. The generated volatiles were subjected to GC-MS analysis and odour evaluation. The effect of encapsulation and storage on the nutty flavour was evaluated. The results revealed that the hydrolysates pretreated (E-HSMP7) or assisted (E-HSMA6) by microwave at 7 and 6min, respectively showed a significant increase in DH. The nutty flavour generated from these hydrolysates (NFMP7 and NFMA6) were dominated with pyrazines whereas, the volatiles from E-HSC (NFC) dominated with furans. NFMA6 showed the highest intensity of nutty and overall acceptability notes, compared with NFMP7 and NFC. Encapsulation resulted in a significant decrease in pyrazines, which are responsible for the nutty note. The significant increase in nutty aroma intensity of the stored encapsulated sample was correlated to the increase in pyrazines.

Tanning capacity of Tessmannia burttii extracts: the potential eco-friendly tanning agents for the leather industry

In the present study, the tannins from stem and root barks of Tessmannia burttii Harms (Caesalpiniaceae), a plant species abundantly growing in Tanzania and other parts of Africa, were investigated for their suitability in hides tanning. Tannin powder was extracted at selected temperatures (30, 50 and 80 °C) and the influence of each temperature on the crosslinking capacity was evaluated. The interaction mechanism between hide powder collagen and the tannins was studied by Differential Scanning Calorimetry (DSC), trinitrobenzensulfonic (TNBS) acid assay and amino acid hydrolysis methods. Extraction temperatures showed low influence on crosslinking capacity of the tannins. However, extract obtained at 50 °C exhibited best performance in terms of gap size between Tonset and Tpeak. The stem bark extract yield was higher than that from the root bark, but both were within the recommended ranges. The tannin content (61%) of T. burttii stem bark extract was above recommended value (10%), whereas its total phenolic content and total flavonoic content were found to be above that of commercial Acacia mearnsii tannin. The study of cross-linking parameters as a function of pH showed cross-linking to occur via a covalent mechanism at the basic amino groups. However, the bonds were not resistant to acid hydrolysis. The observed interaction mechanism indicated that tannins from stem and root barks of T. burttii belong to the condensed tannin, similar to A. mearnsii (black wattle), a commercial tannin source that was used in this study as a reference. Findings from this study depict that T. burttii extracts are auspicious eco-friendly alternative source of vegetable tannins to overcome the use of chromium salts in the leather industry.Graphical abstract

Source, distribution and degradation of sedimentary organic matter in the South Yellow Sea and East China Sea

Sedimentary organic matter (SOM) plays an important role in marine carbon and nitrogen cycling, but the sources, degradation states and fates of SOM are not well understood. In the present study, we determined the total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C), and total hydrolysable amino acids (THAA) to elucidate the sources and degradation states of SOM in the South Yellow Sea (SYS) and the East China Sea (ECS). THAA concentrations ranged from 4.90 to 29.13 μmol/g, with a mean of 11.03 ± 5.06 μmol/g. The distribution pattern of THAA was similar to that of TOC (r = 0.782, P < 0.01) and TN (r = 0.865, P < 0.01), with higher THAA concentrations in the coastal areas. Based on the two end-member mixing model, the fraction of terrestrial organic matter (Ft) ranged from 12.11% to 51.34% (average: 30.17 ± 9.61%), with much higher variability at the nearshore stations compared to the offshore stations. The C/N ratios and the δ13C values showed the different distribution trend, and there was a negative correlation between them (r = −0.479, P < 0.05). Based on the C/N ratios and δ13C values, the SOM in the study area was a mixture of marine organic matter (OM) and soil-derived OM. In addition, our study showed that SOM was dominated by diatomaceous OM compared to carbonate-derived OM and that terrestrial inputs and primary production were the dominant factors controlling the distribution of OM in the study area. Carbon and nitrogen-normalized yields of THAA (THAA-C% and THAA-N%) showed that relatively fresh OM tended to occur in the coastal areas off the Shandong Peninsula. However, the generally low degradation index (DI) values revealed that all SOM in the study area had undergone significant degradation. Glycine increased in relative abundance as the SOM was degraded, while aromatic amino acids (Tyr and Phe) and neutral amino acids (Leu, Ile and Val) had consistently decreasing trends following SOM degradation.

Amino acid and chlorin based degradation indicators in freshwater systems

Lakes cover a global area that is about 35 times smaller than the oceans, but carbon burial in lakes and oceans are on the same order of magnitude. Hence, understanding the processes for such high organic carbon burial in lacustrine systems is essential. We applied proxies typically used for marine environments including amino acid (AA) content and their nitrogen stable isotope composition to the water columns and sediments of three lakes that differ in their trophic states and depositions rates of sedimentary terrestrial organic matter. Additionally, we used carbon isotope fingerprinting of AAs to characterise their sources and fates. We show that this set of proxies tracks sources and degradation processes in eutrophic lakes with high sedimentary total organic carbon and nitrogen content. Those lakes also have a high total hydrolysable amino acid (THAA) content as well as higher pigment concentrations. While the Chlorin degradation Index (CI) showed increasing values with depth, the patterns were less consistent for the Degradation Index (DI). In general, all parameters failed to describe degradation in the most oligotrophic lake due to the very low organic carbon and nitrogen content in the sediment. We show that AAs are mostly of autochthonous origin and that AA contribute 5–45% to the organic material in plankton, POM, and sediment. Proxies based on AA for bacterial reworking (ΣV) or trophic level (TL) showed increasing values in the water column but relatively stable values in the sediments. Furthermore, we show that methanotrophic bacteria led to increased values for the bacterial reworking proxy (ΣV) and extraordinarily low δ13C AA values (−30 to −60‰).

Organic biomarkers and Meiofauna diversity reflect distinct carbon sources to sediments transecting the Mackenzie continental shelf

During the Arctic spring freshet, the Mackenzie River delivers large amounts of dissolved and particulate terrestrial organic carbon to the Canadian Beaufort Sea shelf. This pulse of material and nutrients fuels phytoplankton blooms in late spring and summer and together with under ice primary production contributes to the organic carbon reservoir of the coastal shelf sediments. As a component of the Marine Arctic Ecosystem Study (MARES), samples transecting the Canadian Mackenzie Trough were collected in fall before ice cover to examine the balance of marine and terrestrial carbon in sediments and its relationship with sediment meiobenthic diversity and abundance. Organic biomarker analysis of lipid proxies together with total hydrolyzable amino acids (THAA) defined organic matter sources and potential lability. Across the shelf transect, consistent values observed in sedimentary total organic carbon (1.09%–1.62%) belied a shift in the balance of terrestrial and marine carbon sources. Predominately terrestrial inputs at the shallow site near the delta outflow appeared to constrain meiofaunal populations while the deepest location off shelf reflected lower labile marine organic carbon reaching the sediments that limited benthic production. Surface sediments at the mid-shelf, however, showed a near 3-fold increase (to 1.16 mg C OC-1) in contributions by diatoms and dinoflagellates markers plus a peak in total amino acids (9.53 mg g OC-1) which corresponded with higher meiofauna abundance. The combination of detailed organic analysis together with meiofaunal community measures suggest that mid-shelf sediments receive higher contributions of labile marine carbon which drive increased meiofauna diversity and abundance despite the large background of terrestrial organic material exiting the Mackenzie River outflow.

Aminopeptidase Expression in Multiple Myeloma Associates with Disease Progression and Sensitivity to Melflufen.

Simple SummaryThe aims of this study were to investigate aminopeptidase expression in multiple myeloma and to identify the aminopeptidases responsible for the activation of the peptide–drug conjugate melflufen in multiple myeloma. We observed a differential expression of aminopeptidases between relapsed/refractory and newly diagnosed multiple myeloma patients. A higher expression of the aminopeptidase genes XPNPEP1, RNPEP, DPP3, and BLMH in multiple myeloma plasma cells was associated with shorter patient overall survival. The peptide–drug conjugate melflufen was particularly active towards plasma cells from relapsed/refractory multiple myeloma patients. Melflufen could be hydrolyzed to its active form by the aminopeptidases LAP3, LTA4H, RNPEP, and ANPEP, all of which are expressed in multiple myeloma. These results indicate critical roles for aminopeptidases in disease progression and the activity of melflufen in multiple myeloma.Multiple myeloma (MM) is characterized by extensive immunoglobulin production leading to an excessive load on protein homeostasis in tumor cells. Aminopeptidases contribute to proteolysis by catalyzing the hydrolysis of amino acids from proteins or peptides and function downstream of the ubiquitin–proteasome pathway. Notably, aminopeptidases can be utilized in the delivery of antibody and peptide-conjugated drugs, such as melflufen, currently in clinical trials. We analyzed the expression of 39 aminopeptidase genes in MM samples from 122 patients treated at Finnish cancer centers and 892 patients from the CoMMpass database. Based on ranked abundance, LAP3, ERAP2, METAP2, TTP2, and DPP7 were highly expressed in MM. ERAP2, XPNPEP1, DPP3, RNPEP, and CTSV were differentially expressed between relapsed/refractory and newly diagnosed MM samples (p < 0.05). Sensitivity to melflufen was detected ex vivo in 11/15 MM patient samples, and high sensitivity was observed, especially in relapsed/refractory samples. Survival analysis revealed that high expression of XPNPEP1, RNPEP, DPP3, and BLMH (p < 0.05) was associated with shorter overall survival. Hydrolysis analysis demonstrated that melflufen is a substrate for aminopeptidases LAP3, LTA4H, RNPEP, and ANPEP. The sensitivity of MM cell lines to melflufen was reduced by aminopeptidase inhibitors. These results indicate critical roles of aminopeptidases in disease progression and the activity of melflufen in MM.

Temporal and spatial distribution of dissolved amino acids in the surface microlayer and subsurface water of the Bohai Sea and the Yellow Sea

Concentrations of total hydrolyzed amino acids (THAA) and chlorophyll a (Chl-a) in the Bohai Sea (BS) and Yellow Sea (YS) were determined from August to September 2015 (summer) and from January to February 2016 (winter). The average concentrations of THAA in the surface microlayer and subsurface water in the study area were 2.92 (1.14 to 7.31) and 1.64 (0.49 to 3.32) μmol/L in summer, respectively, and 1.01 (0.69 to 1.70) μmol/L in the subsurface water during winter. The spatial distributions of THAA were obviously influenced by phytoplankton biomass and terrestrial input, while vertical distributions of THAA were mainly affected by circulation and phytoplankton. The main constituents of THAA were aspartic acid (Asp), glycine (Gly), serine (Ser), glutamic acid (Glu) and alanine (Ala) during summer and winter. THAA and Chl-a were more abundant in the surface microlayer than in the subsurface water, with average enrichment factors (EFs) of 2.01 and 2.06, respectively. Enrichment of THAA and Chl-a in the surface microlayer is the result of a combination effect, such as the influence of phytoplankton, wind action and mixing processes. This research may have implications for the distribution, enrichment and source of THAA in the BS and YS.

Dissolved free, total and particulate enantiomeric amino acid levels in eutrophic and oligotrophic parts of a semi-enclosed bay (İzmir, Aegean Sea)

Seasonal variations of dissolved free, total and particulate enantiomeric amino acids were investigated in eutrophic (middle–inner) to oligotrophic (outer) parts of the İzmir Bay. Mean dissolved free, dissolved combined, total dissolved hydrolysable and particulate hydrolysable amino acid levels in middle–inner parts were higher than that of outer part, and found as 232.5, 757.3, 989.8 and 20.9 nM, respectively. Among all amino acid forms, highest mol percentages were found for glycine and L-glutamate. Total D-enantiomers in all forms were only present at trace amounts (≤10%). While dissolved organic carbon and nitrogen enriched with freshly produced dissolved amino acids especially in spring, degradation processes were dominant in summer and autumn. According to degradation index of DFAA, seasonal production and degradation were balanced in eutrophic middle–inner bays. On the other hand, seasonally constant fresh production was observed in oligotrophic outer bay. Seasonal and spatial variations of amino acids and organic matter pools in eutrophic and oligotrophic waters of İzmir Bay were under the influences of autochthonous and allochthonous processes.

Organic matter degradation state affects dissimilatory nitrate reduction processes in Knysna estuarine sediment, South Africa

The quality of organic matter influencing sediment nitrate (NO3−) reduction processes in estuarine zones is not well understood. This study aimed to assess the denitrification (DNF), anaerobic ammonium oxidation (ANA), and dissimilatory reduction of nitrate to ammonium (DNRA) in estuarine zones of South Africa, and to understand the effects of organic matter fractions and degradation states on anaerobic NO3− reduction processes. We measured the anaerobic NO3− reduction process rates using 15N isotope-tracing techniques in Knysna Estuary, South Africa. Total hydrolyzable amino acids and fractions and geochemical parameters were also measured. The correlation analysis and structural equation model were used to evaluate the key environmental factors driving NO3− reduction processes. Potential DNF, ANA, and DNRA rates in Knysna Estuary varied from 3.59 to 16.62, 0.28 to 1.16, and 1.52 to 8.38 nmol g−1 h−1, respectively, with a large spatial variation. The variations in NO3− reduction process rates can largely be explained by sediment water content, dissolved organic carbon, and amino acid–based degradation index, while the total organic carbon and inorganic nitrogen contents were not related to the NO3− reduction processes. The DNF process contributed 47.28–79.34% total NO3− reduction, as compared to 17.59–47.58% for DNRA and 2.53–5.76% for ANA. The retention of reactive nitrogen (N) attributed to the DNRA process was approximately 42 t N km−2 year−1. This study reported the first simultaneous investigation of the anaerobic NO3− reduction processes in estuarine areas of South Africa, implying that the qualities of substrate were more important in regulating NO3− reduction processes than substrate quantities and highlighting that DNRA played an important role in reactive N retention.

Pathways and mechanisms of nitrogen transformation during co-composting of pig manure and diatomite

The aim of this study was to investigate the pathways and mechanisms of nitrogen transformation during the composting process, by adding diatomite (0%, 2.5%, 5%, 10%, 15% and 20%) into initial mixtures of pig manure and sawdust. The results revealed that diatomite facilitated the conversion from NH4+-N to amino acid nitrogen and hydrolysis undefined nitrogen, then reduced NH3 and N2O emission by 8.63–35.29% and 14.34–73.21%, respectively. Moreover, the structure and abundance of nitrogen functional genes provided evidence for nitrogen loss. Furthermore, compared with the control (0.03), the treatment blended with 10% diatomite (T3) had the highest value in composting score (-1.27). Additionally, the ratio of carbon and nitrogen (57.30%) was vital for reducing nitrogen loss among all physio-chemical parameters in this study. In conclusion, adding diatomite was a practical way to enhance nitrogen conservation and increase quality of end products, and the optimum added dosage was at 10%.

Seasonal Variation, Degradation, and Bioavailability of Dissolved Organic Matter in the Changjiang Estuary and its Adjacent East China Sea

AbstractSystematic surveys to examine seasonal variation, degradation, and bioavailability of dissolved organic matter (DOM) in the Changjiang Estuary and the adjacent East China Sea were conducted in July 2016 and February 2017. Concentrations of dissolved organic carbon (DOC) and total hydrolyzable amino acids (THAA) were higher in July than in February. THAA and chlorophyll a (Chl‐a) were positively correlated in July, but not in February. The carbon normalized yields of THAA (THAA‐C%) in surface waters in July and February were not significantly different. However, degradation index (DI) values in the surface water were higher in February than in July. Compared with outer estuary, the inner estuary had lower THAA‐C% and DI values in both surveys. Solar radiation experiments showed that THAA and THAA‐C% values increased with time at station A6‐11 in the oceanic water but declined at C3 in the freshwater, possibly due to the different origins, chemical compositions, or initial degradation states of the DOM at the time of collection. Microbial incubation experiments showed that accumulated DOC and DON in surface waters were bioavailable to the microbial community of the surface layer, but recalcitrant to the microbial fauna from the bottom layer. Leucine (Leu) was selectively consumed, while glycine (Gly), threonine, and alanine appeared to be recalcitrant in summer (July) microbial incubations; and histidine, Gly, and methionine were preferentially consumed, while aspartic acid, serine, phenylalanine, and Leu were recalcitrant in winter (February) incubations.

Measurement report: Hydrolyzed amino acids in fine and coarse atmospheric aerosol in Nanchang, China: concentrations, compositions, sources and possible bacterial degradation state

Abstract. Amino acids (AAs) are relevant for nitrogen cycles, climate change and public health. Their size distribution may help to uncover the source, transformation and fate of protein in the atmosphere. This paper explores the use of compound-specific δ15N patterns of hydrolyzed amino acid (HAA), δ15N values of total hydrolyzed amino acid (δ15NTHAA), degradation index (DI) and the variance within trophic AAs (∑V) as markers to examine the sources and processing history of different sizes of particle in the atmosphere. Two weeks of daily aerosol samples from five sampling sites in the Nanchang area (Jiangxi Province, China) and samples of main emission sources of AAs in aerosols (biomass burning, soil and plants) were collected (Zhu et al., 2020). Here, we measured the concentrations and δ15N values of each HAA in two size-segregated aerosol particles (&gt; 2.5 µm and PM2.5). Our results showed that the average concentrations of THAA in fine particles was nearly 6 times higher than that in coarse particles (p &lt; 0.01) and composition profiles of fine and coarse particles were quite different from each other. The δ15N values of hydrolyzed glycine and THAA in both fine and coarse particles were typically in the range of those from biomass burning, soil and plant sources. Moreover, the average difference in the δ15NTHAA value between fine and coarse particles was smaller than 1.5 ‰. These results suggested that the sources of atmospheric HAAs for fine and coarse particles might be similar. Meanwhile, compared to fine particles, significantly lower DI values (p &lt; 0.05), “scattered” δ15N distribution in trophic AA and higher ∑V values (p &lt; 0.05) were observed in coarse particles. But the difference in δ15N values of source AA (glycine, serine, phenylalanine and lysine) and THAA between coarse particles and fine particles was relatively small. It is likely that AAs in coarse particles have advanced bacterial degradation states compared to fine particles. Besides that, the significant increase in DI values and a decrease in ∑V values for coarse particles were observed on days on which precipitation fell (p &lt; 0.05). This implies that “fresh” AAs in coarse particles were likely released following the precipitation.