Carbon Nitrogen Source Research Articles

Optimization of Growth Medium of Bacillus sp. TTMP20 by Response Surface Methodology

High-density culture is able to obtain high concentration and activity of microbes, which is a key technology for fermentation industry. This will greatly shorten fermentation cycle and reduce production cost. Bacillus sp. TTMP20 is a strain with a high yield of 2,3,5,6-tetramethylpyrazine (TTMP). In this study, the growth medium of Bacillus sp. TTMP20 was optimized. Different carbon/nitrogen sources were investigated, and the best carbon source (glucose) and nitrogen source (yeast extract) was determined. With the concentrations of glucose, yeast extract and pH as influence factors, response surface method was used to optimize the above-mentioned influence factors to maximize cell density of the strain. The optimal growth medium is as follows: 4 g/L of yeast extract, 15.754 g/L of glucose, 2 g/L of K2HPO4, 10 g/L of NaCl, and 6.50 of pH. The predicted and actual maxima are 1.388 and 1.3, respectively. This is 61.4% higher than the cell density of the basic medium. This will provide the adequate seed culture for the subsequent fermentation of TTMP, and improve the application level of Bacillus sp. TTMP20.

Novel Phospholipase C with High Catalytic Activity from a Bacillus stearothermophilus Strain: An Ideal Choice for the Oil Degumming Process

A novel thermoactive phosphatidylcholine-specific phospholipase C (PC-PLCBs) was identified from Bacillus stearothermophilus isolated from a soil sample from an olive oil mill. Enhanced PLCBs production was observed after 10 h of incubation at 55 °C in a culture medium containing 1 mM of Zn2+ with an 8% inoculum size and 6 g/L glucose and 4/L yeast extract as the preferred carbon energy and nitrogen sources, respectively. PLCBs was purified to homogeneity by heat treatment, ammonium sulfate fractionation, and anion exchange chromatography, resulting in a purification factor of 17.6 with 39% recovery. Interestingly, this enzyme showed a high specific activity of 8450 U/mg at pH 8–9 and 60 °C, using phosphatidylcholine PC as the substrate, in the presence of 9 mM sodium deoxycholate and 0.4 mM Zn2+. Remarkable stability at acidic and alkali pH and up to 65 °C was also observed. PLCBs displayed a substrate specificity order of phosphatidylcholine > phosphatidylethanolamine > phosphatidylserine > sphingomyelin > phosphatidylinositol > cardiolipin and was classified as a PC-PLC. In contrast to phospholipases C previously isolated from Bacillus strains, this PLCBs substrate specificity was correlated to its hemolytic and anti-bacterial potential against erythrocytes and Gram-positive bacterial membranes, which are rich in glycerophospholipids and cardiolipin. An evaluation of PLCBs soybean degumming process efficiency showed that the purified enzyme reduced the phosphorus content to 35 mg/kg and increased the amount of diacylglycerols released, indicating its ability to hydrolyze phospholipids in the crude soybean oil. Collectively, PLCBs could be considered as a potential catalyst for efficient industrial oil degumming, advancing the edible oil industry by reducing the oil gum volume through transforming non-hydratable phospholipids into their hydratable forms, as well as through generating diacylglycerols, which are miscible with triacylglycerols, thereby reducing losses.

Effects of Lacticaseibacillus paracasei SNB-derived postbiotic components on intestinal barrier dysfunction and composition of gut microbiota

The bacterial surface components are considered as effector molecules and show the potential to support intestinal health, but the detailed mechanism of how the gut microbiota changes after the intervention of surface molecules is still unknown. In the present study, capsular polysaccharide (B-CPS) and surface layer protein (B-SLP) were extracted from Lacticaseibacillus paracasei S-NB. The protective effect of direct administration of B-CPS (100 μg/mL) and B-SLP (100 μg/mL) on intestinal epithelial barrier dysfunction was verified based on the LPS-induced Caco-2 cell model. Additionally, the B-CPS and B-SLP could be utilized as carbon source and nitrogen source for the growth of several Lactobacillus strains, respectively. The postbiotic potential of B-CPS and B-SLP was further evaluated by in vitro fermentation with fecal cultures. The B-CPS and a combination of B-CPS and B-SLP regulated the composition of gut microbiota by increasing the relative abundances of Bacteroides, Bifidobacterium, Phascolarctobacterium, Parabacteroides, Subdoligranulum and Collinsella and decreasing the abundance of pathogenic bacteria like Escherichia-Shigella, Blautia, Citrobacter and Fusobacterium. Meanwhile, the total short-chain fatty acid production markedly increased after fermentation with either B-CPS individually or in combination with B-SLP. These results provided an important basis for the application of B-CPS and B-SLP as postbiotics to improve human intestinal health.

Lithium storage of SnP2O7 anode coated by N-doped carbon and anchored on P-doped carbon framework

N-doped carbon-coated SnP2O7 anodes anchored on P-doped carbon framework (SPO/C-P@C-N) have been successfully synthesized via a novel and environmentally friendly method, using a green raw material of phytic acid as phosphorus and carbon sources, and dimethylimidazole as the second carbon source and nitrogen source. N-doped carbon coating and P-doped carbon framework inhibit the volume shrinkage and expansion, improve the electronic conductivity and diffusion coefficient of Li+ ions as well as capacitive contribution ratio, reduce the charge transfer resistance and the particle size, and then enhance the electrochemical performance of SPO/C-P@C-N. SPO/C-P@C-N-1.2 with the carbon content of 18.5 wt% exhibits excellent electrochemical performance. The discharge specific capacity is 416.6 mAh/g at 0.5 A/g after 200 cycles. 234.3 mAh/g is kept at 2 A/g for the 1000th cycle. In addition, the discharge specific capacity of the LiNi0.5Mn1.5O4//SPO/C-P@C-N-1.2 full cell is 206.6 mAh/g for the 200th cycle at 0.5C in 1.4–4.4 V. The full cell can power green, red, blue, and orange light-emitting diode (LED) bulbs, as well as LED small light strings and heart-shaped circuit boards. It is the first report on SnP2O7 successfully applied to full cells, demonstrating the potential application.

Improved production of lactiplantibacillus plantarum RO30 exopolysaccharide (REPS) by optimization of process parameters through statistical experimental designs

BackgroundIn investigating of (exopolysaccharide) EPS from unconventional sources, lactic acid bacteria have a vital role due to their generally recognized as safe (GRAS) status. EPSs have diverse applications such as drug delivery, antimicrobial activity, surgical implants, and many more in many sectors. Despite being important, the main hindrance to the commercial application of these significant biopolymers is low productivity. Therefore, this study primarily focuses on optimizing physio-chemical conditions to maximize the previously produced EPS from probiotic Lactiplantibacillus plantarum RO30 (L. plantarum RO30) using one factor at a time (OFAT) and method Response Surface Methodology (RSM).ResultsThe EPS obtained from L. plantarum RO30 named REPS. The medium formulation for REPS production using the OFAT method revealed that sucrose (20 g/L, beef extract (25 g/L), and ammonium sulfate at 4 g/L concentration were the optimum carbon, organic and inorganic nitrogen sources, and REPS yield was increased up to 9.11 ± 0.51 g/L. RSM experiments revealed that, a greatly significant quadratic polynomial attained from the Central Composite Design (CCD) model was fruitful for specifying the most favorable cultural conditions that have significant consequences on REPS yield. The maximal amount of REPS (10.32 g/L) was formed by: sucrose (40 g/L), beef extract (25 g/L), pH (5.5), incubation temperature (30 °C), and incubation period (72 h). A high closeness was obtained between the predicted and experimental values and it displayed the efficiency of the RSM.ConclusionThis study was conducted to reinforce REPS production in the probiotic LAB L. plantarum RO30 by utilizing various experimental parameters. The maximum REPS yield of 10.32 g/L was attained under the circumstances optimized in the study.

One-step facile growth of nitrogen-doped graphene nanowalls by catalyst-free thermal chemical vapor deposition

We report an effective technique for the growth of graphene nanowalls (GNWs) and nitrogen-doped graphene nanowalls (N-GNWs) using a thermal chemical vapor deposition (TCVD) on the catalyst-free substrate. Ethanol and mixed ethanol-imidazole were used as carbon and carbon-nitrogen sources for the growth of GNWs and N-GNWs, respectively. The effect of imidazole concentration on the morphology, nanostructure, crystal structure, crystallinity, chemical bonding and chemical structure of GNWs and N-GNWs were investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. Focused ion beam combined with TEM was utilized to analyze the growth mechanism. The results show that GNWs and N-GNWs are vertically oriented graphene nanosheets on in-plane-oriented graphitic layer/carbon nanolayer. An increase in imidazole concentration from 2.5 to 5.0 wt% increases the nitrogen content in the N-GNWs from 1.24 to 2.61 at%. The incorporated nitrogen atoms are mainly graphitic-N. One-step facile growth of N-GNWs by TCVD method without the need for a metal catalyst and plasma system was achieved.

Effect of pH, Temperature, Nutrients and incubation time on production of xanthan gum byXanthomonas campetrisand Stenotrophomonas maltophilia

This study screened Xanthomonasspecies isolated from tomato, pepper, mango and banana with black rot spots for potential to produce xanthan gum. The leaves were washed in normal saline and tenfold dilution was prepared. Aliquots (1ml) were plated on Nutrientagar and incubated at 25 ̊C for 48h. Colonies with yellow pigmentation were gram stained. Gram negative rod bacteria were subjected to emulsification test. Isolates with yellow colonies, gram negative rods and which exhibited stable emulsion in carbon enriched medium were regarded as potential xanthan gum producers. Eight (61.5%) of the isolates screened fulfilled these conditions. Biochemical tests on the isolates revealed that the organisms were Xanthomonasspecies and were coded accordingly (BX2, BX3, PX4, MX6, PX7,MX8, TM9, TX11). The best two isolates (TM9 and BX3) were subjected to molecular analysis and were found to be Xanthomonas campestris and Stenotrophomonas maltophilia. Xanthomonas campestrisand Stenotrophomonas maltophilia were more efficient xanthan gum producers, yielding 2.10 g/l and 1.63 g/l respectively of xanthan gum after 96 h. The results revealed that as the fermentation time increased, the biomass also increased. The xanthan gum yield by the two organisms was found to increase from 0.92 to 7.6 g/l and 0.99 to 4.55 g/l under optimized conditions of pH: (9.0, 7.0), temperature (25°C) carbon source (02% pineapple peels 0.2% sugarcane bagasse) and nitrogen source (Yeast extract) respectively. The result suggest that Xanthomonasspecies are good candidates for xanthan gum production.

Production kinetics and characterization of natural food color (torularhodin) with antimicrobial potential

The present investigation was conducted to optimize the fermentative production of food color (carotenoid pigments) using Rhodotorula sp. grown under batch cultivation. The effect of different carbon sources, nitrogen source and pH on carotenoid yield was investigated initially. The maximum carotenoid yield of 3520.23 and 2992.65 μg/g were obtained using sorbitol and beef extract as potential carbon and nitrogen sources, respectively, at pH 7.0. Further, process optimization was done using RSM to enhance the carotenoid yield. The optimized condition comprised; 2.0 g/L sorbitol, 0.32 g/L beef extract and 6.25 pH. Optimized condition scale-up in 7.5 L bioreactor (working volume 3.0 L) gave maximum carotenoid and biomass yield of 7325.70 ± 0.04 μg/g and 0.589 ± 0.05 g/L, respectively, after 48 h of cultivation. Leudking Piret model deduced mixed growth associated carotenoid production. The carotenoid pigment was characterized as torularhodin by FTIR and showed antimicrobial activities against E. coli and S. aureus.

Rapid biosynthesis of biosurfactants by Bacillus tequilensisSL9 isolated from oily sludge: Characterization, optimization, and potential applications

AbstractThe demand of biosurfactants is increasing. It is of great significance to obtain nonpathogenic and high‐yielding microorganisms for the industrial‐scale production of biosurfactants. A biosurfactant‐producing strain SL9 was isolated from oily sludge. It was identified as Bacillus tequilensis based on colonial morphology and 16S rDNA sequence analysis. The biosurfactants produced by strain SL9 was extracted by modified acid precipitation method. A mixture of C12, C13, C14 and C15 surfactin homologues was detected based on HPLC–MS analysis. The optimum production of biosurfactants occurs at pH 7.0 and in the presence of 1.0 g/L NaCl. The optimal carbon source and nitrogen source were 40.0 g/L sucrose and 4.0 g/L NaNO3, respectively. The maximum yield of biosurfactants from strain SL9 was up to 1332.68 mg/L. Interestingly, B. tequilensis SL9 can rapidly synthesize biosurfactants with a yield of 739.36 mg/L in 12 h. The extracted biosurfactants reduced the surface tension of water from 72.1 to 27.5 mN/m with a CMC of 33 mg/L. The biosurfactants can also emulsify paraffin with a EI24 value of 57.58% and keep this good emulsifying activity after 96 h. The produced biosurfactants showed antimicrobial activities against Staphylococcus aureus, Cladosporium sp. and Alternaria sp. with inhibitory rate of 75.67%, 59.07% and 22.91%, respectively. The isolated strain B. tequilensis SL9 can be a nonpathogenic producer for rapid biosynthesis of biosurfactants with a relative high yield. Strain SL9 and its biosurfactant products are promising for application in the oil exploration, bioremediation, agricultural biocontrol, and pharmaceutical industries.

Metabolic insights into how multifunctional microbial consortium enhances atrazine removal and phosphorus uptake at low temperature

Agricultural soils in the black soil region of northeast China often face negative stress due to low temperatures, pesticide contamination, and inadequate nutrient supply. In this study, a new cold-tolerant strain of Peribacillus simplex C1 (C1) was selectively isolated from atrazine contaminated soil. The artificially constructed microbial consortium (CPD) [C1, phosphorus-solubilizing bacterium Enterobacter sp. P1, and atrazine-degrading bacterium Acinetobacter lwoffii DNS32] demonstrated the most effective performance in enhancing atrazine degradation and phosphorus-solubilizing capacity when the initial inoculation ratio of 5:1:2 at 15 °C. CPD enhanced energy-related metabolic pathways and increased choline production to regulate bacterial adaptation to temperature decrease. Additionally, the strains could selectively utilize carbon sources (low molecular weight organic acids) or nitrogen sources (some metabolites of atrazine) provided by each other to enhance growth. Furthermore, strain C1 enhanced membrane fluidity through increased expression of the unsaturated fatty acids. Pot experiments demonstrated that CPD assisted soybean seedlings in resisting dual stresses of low temperature and atrazine contamination by inducing the expression of genes related to photosynthesis, membrane permeability, phosphorus response, and cold tolerance.

Rapid Preparation of Long-Wavelength Emissive Carbon Dots for Information Encryption Using the Microwave-Assisted Method.

The synthesis of long-wavelength emission fluorescent carbon dots is not common, and it is even more difficult to quickly synthesize within 10 min. In this experiment, yellow, orange, and red B, N codoped fluorescent carbon dots were successfully synthesized using a microwave-assisted method with o-phenylenediamine as the carbon-nitrogen source, boric acid as the boron source, and potassium chloride as the catalyst in just 7 min. Based on the different contents of B, N element doping, there are differences in their surface structures, resulting in differences in the luminescence properties of the synthesized carbon dots. Long-wavelength carbon dots can avoid interference from the blue fluorescence of filter papers and have a clearer display in information encryption. Therefore, three types of carbon dots were mixed with PVP to produce fluorescent inks, and anticounterfeiting and encryption patterns were designed on the filter paper, displaying different fluorescence information under sunlight and UV light. In addition, the rich fluorescent colors were combined ingeniously to enable secondary encryption of information in the form of binary codes that increase the difficulty of decoding. These indicate that the three synthesized long-wavelength carbon dots have good application prospects in information encryption.

Effect of pH, Carbon and Nitrogen Sources on Antibiotic Production by Actinomycetes Isolates from River Tana and Lake Elementaita, Kenya

The escalating concern over antibiotic resistance and its profound impact on public health have underscored the urgent need to explore alternative reservoirs of antimicrobial agents. In this regard, Actinomycetes have emerged as a compelling area of investigation due to their remarkable capacity to produce bioactive compounds. Therefore, this study sought to investigate the influence of pH and various carbon and nitrogen sources on the antibacterial activity of Actinomycetes isolates collected from Lake Elementaita and River Tana. By examining the effects of these factors, we aimed to gain insights into the optimization of growth conditions and nutrient availability to enhance the production of bioactive compounds with potent antibacterial properties. The Actinomycetes isolates used in this study were from Lake Elementaita and River Tana, known for their diverse ecological characteristics and potential as sources of bioactive compounds. The isolates were subjected to morphological, biochemical, and molecular techniques to ensure accurate identification. To assess the antibacterial activity of the Actinomycetes isolates, they were tested against E. coli using the agar well diffusion method. The independent variables examined in this study were pH levels (4, 7, and 9) as well as different carbon sources (fructose and sucrose) and nitrogen sources (urea and sodium nitrate). The diameter of the inhibition zones served as the dependent variable. The data collected on the effects of pH and nutrients on the inhibition zones of Actinomycetes isolates were subjected to statistical analysis. One-way ANOVA was performed to assess significant differences in antibacterial activity among the isolates under different carbon and nitrogen preference. Mean values were compared using the LSD test at a significance level (α) of 0.05. Furthermore, the Kruskal-Wallis test was utilized to analyze the pH preferences of the Actinomycetes isolates at a significance level (α) of 0.05. The results showed that pH significantly influenced the bioactivity of the Actinomycetes isolates, with pH 7 exhibiting the highest inhibition zones against E. coli. The isolates displayed varied antibacterial activities depending on the carbon and nitrogen sources provided. Sucrose was the most preferred carbon source, followed by fructose, while urea was the preferred nitrogen source, followed by sodium nitrate. The study concluded that pH and nutrient availability play crucial roles in determining the antibacterial activity of Actinomycetes isolates. Other than contributing to our in-depth understanding of the factors influencing the antimicrobial potential of Actinomycetes, the results of this study highlight the importance of optimizing growth conditions and nutrient availability to enhance the production of bioactive compounds with potent antibacterial properties. Further investigations and exploration of Actinomycetes from diverse environments are recommended to discover new bioactive molecules for combating antibiotic resistance.

Application of OFAT approach for optimizing tannase production under submerged fermentation

Current study reports the optimization of tannase production by Bacillus haynesii SSRY4MN031245 by employing One factor at a Time approach (OFAT). The effects of supplementary carbon sources, nitrogen sources, inoculum size and substrate (Tannic acid) concentration were studied on enzyme production. Tannic acid, when added optimally in the production media along with optimized inoculum size and optimized concentrations of glucose, sodium nitrate resulted in improved tannase production. Optimization of 2.85-fold was achieved by OFAT strategy.

Effects of Main Nutrient Sources on Improving Monascus Pigments and Saccharifying Power of Monascus purpureus in Submerged Fermentation

Hong Qu (HQ), obtained through fermentation of various grains using Monascus spp., has been widely utilized as the main and characteristic initial saccharification and traditional fermentation starter in the food brewing industry. The quality, color, and flavor of HQ and HQ wine are closely related to the saccharifying power (SP) and Monascus pigments (MPs) of Monascus spp. In this study, to optimize the culture medium in submerged fermentation by M. purpureus G11 for improving SP and MPs, the effects of carbon source, nitrogen source, inorganic salts, and vitamins on SP activity and biosynthesis of MPs were explored through single-factor analysis and response surface Box–Behnken experiments. The results showed that the optimal medium composition was 6.008% rice powder, 1.021% peptone, 0.0049% CuSO4, and 0.052% vitamin B1. Validation experiments performed under the optimized fermentation conditions showed a significant increase in MPs and SP by 14.91% and 36.24%, with maximum MPs and SP reaching 112.61 and 365.12 u/mL, respectively. This study provides a theoretical basis for enhancing MPs and SP in M. purpureus for HQ production, to improve the production efficiency and shorten the production cycle of HQ-related fermentation products.

Helical chiral carbon nanotubes loaded with highly dispersed ultra-small cobalt-iron-platinum alloy composites for oxygen evolution and oxygen reduction reaction

In this study, we successfully prepared CH-CNT@Fe-Co-Ptx by combining chiral helical nanostructure, high conductivity, high electro-catalytic activity of iron-cobalt transition metals and precious platinum. The material used C18-L-Clu as the soft template, polypyrrole as the carbon source and nitrogen source. The precursor cobalt iron ions were then loaded onto the chiral amino acid template. Using the displacement reaction, a spot of platinum metal was successfully introduced into the composite to obtain CH-CNT@Fe-Co-Ptx composite material. According to the reaction mechanism steps of OER/ORR in alkaline solution, Fe-Co-Pt as the active site adsorbed OH- in OER and adsorbed H2O molecules in ORR. The tafer slope of OER and ORR for catalyst CH-CNT@Fe-Co-Pt2 reached 35.0 mV dec−1 and 60.8 mV dec−1, respectively. And the current density of H-CNT@Fe-Co-Pt2 retained 84% and 91.5 % respectively after a long time i-t test. Moreover, the number of transferred electrons of CH-CNT@Fe-Co-Pt2 in the ORR reaction reaches 3.90. This work provides new ideas for the research of chiral carbon nanomaterials in the field of electro-catalytic energy, and provides a new method for the development of efficient and low-cost energy electro-catalysts.

Development of a green fermentation strategy with resource cycle for the docosahexaenoic acid production by Schizochytrium sp.

The fermentation production of docosahexaenoic acid (DHA) is an industrial process with huge consumption of freshwater resource and nutrient, such as carbon sources and nitrogen sources. In this study, seawater and fermentation wastewater were introduced into the fermentation production of DHA, which could solve the problem of fermentation industry competing with humans for freshwater. In addition, a green fermentation strategy with pH control using waste ammonia, NaOH and citric acid as well as FW recycling was proposed. It could provide a stable external environment for cell growth and lipid synthesis while alleviating the dependence on organic nitrogen sources of Schizochytrium sp. It was proved that this strategy has good industrialization potential for DHA production, and the biomass, lipid and DHA yield reached to 195.8 g/L, 74.4 g/L and 46.4 g/L in 50 L bioreactor, respectively. This study provides a green and economic bioprocess technology for DHA production by Schizochytrium sp.

Enhanced extracellular production of raw starch-degrading α-amylase in Bacillus subtilis through expression regulatory element modification and fermentation optimization

BackgroundRaw starch-degrading α-amylase (RSDA) can hydrolyze raw starch at moderate temperatures, thus contributing to savings in starch processing costs. However, the low production level of RSDA limits its industrial application. Therefore, improving the extracellular expression of RSDA in Bacillus subtilis, a commonly used industrial expression host, has great value.ResultsIn this study, the extracellular production level of Pontibacillus sp. ZY raw starch-degrading α-amylase (AmyZ1) in B. subtilis was enhanced by expression regulatory element modification and fermentation optimization. As an important regulatory element of gene expression, the promoter, signal peptide, and ribosome binding site (RBS) sequences upstream of the amyZ1 gene were sequentially optimized. Initially, based on five single promoters, the dual-promoter Pveg-PylB was constructed by tandem promoter engineering. Afterward, the optimal signal peptide SPNucB was obtained by screening 173 B. subtilis signal peptides. Then, the RBS sequence was optimized using the RBS Calculator to obtain the optimal RBS1. The resulting recombinant strain WBZ-VY-B-R1 showed an extracellular AmyZ1 activity of 4824.2 and 41251.3 U/mL during shake-flask cultivation and 3-L fermenter fermentation, which were 2.6- and 2.5-fold greater than those of the original strain WBZ-Y, respectively. Finally, the extracellular AmyZ1 activity of WBZ-VY-B-R1 was increased to 5733.5 U/mL in shake flask by optimizing the type and concentration of carbon source, nitrogen source, and metal ions in the fermentation medium. On this basis, its extracellular AmyZ1 activity was increased to 49082.1 U/mL in 3-L fermenter by optimizing the basic medium components as well as the ratio of carbon and nitrogen sources in the feed solution. This is the highest production level reported to date for recombinant RSDA production.ConclusionsThis study represents a report on the extracellular production of AmyZ1 using B. subtilis as a host strain, and achieved the current highest expression level. The results of this study will lay a foundation for the industrial application of RSDA. In addition, the strategies employed here also provide a promising way for improving other protein production in B. subtilis.

Identification and characterization of pathogens causing saffron corm rot in China.

Corm rot is the most important disease of saffron, for which fungi from several genus such as Fusarium spp. Penicillium spp. and Botrytis spp., have been previously reported to be the pathogens. In this research, we used a combination of amplicon sequencing and traditional isolation methods to identify the causal agents, main infection source. The diversity of microbial communities in diseased saffron corms and soil decreased significantly compared with healthy corms and soil. The contents of Penicillium and Botrytis in healthy and diseased corms were similarly high, indicating that them were not directly related to the occurrence of corm rot. But the relative abundance of Fusarium, Cadophora and Fusicolla were significantly higher in the diseased corms than healthy ones. The abundance of Fusarium increased, while the abundance of Oidiodendron, Paraphaeosphaeria and the endophytic beneficial bacteria Pseudomonas decreased, which may relate to the occurrence of the disease. The co-occurrence network diagram showed that the correlation between fungal and bacterial communities was mainly positive. Plant pathogens were relatively abundant in the diseased soil, according to functional gene prediction. At the same time, we also collected 100 diseased corms from the fields in Jiande, where is known as the "hometown of saffron." All isolated pathogenic strains were identified as Fusarium oxysporum through morphological observation and phylogenetic tree analysis of ITS, Tef-1α and β-tubulin. To better clarify the biological characteristics of F. oxysporum, we cultured the isolates at different temperatures and pH values. The optimum temperature for mycelial growth and sporulation was 25°C, pH 6，carbon sources sorbitol and nitrogen sources, peptone. In short, our results suggests that F. oxysporum was the pathogen causing corm rot in Jiande and corms other than soils are the main primary infection source. These new understanding of saffron corm rot will provide the theoretical basis for its better and efficiently management.

Two strains of bacteria from oilfield slickwater and their performance in partially hydrolyzed polyacrylamide biodegradation

Partially hydrolyzed polyacrylamide (HPAM) is widely used in oil recovery, but the HPAM residues also induce environmental pollution. In this study, two strains of bacteria, SCE2 and NMYGYB4, have been isolated from oilfield slickwater and identified as Tistrella bauzanensis (SCE2) and Brucella sp. (NMYGYB4). The optimal biodegradation conditions of Tistrella bauzanensis SCE2 were inoculation time 36 h, shaking speed 175 rpm, inoculum amount 3% (v/v), pH 3.0, and incubation temperature 37 °C with urea and glucose as the nitrogen and carbon sources. And the optimal biodegradation conditions of Brucella sp. NMYGYB4 were 12 h, 185 rpm, 2% (v/v), pH 7.0 and 37 °C with yeast powder and sucrose as the nitrogen carbon sources. HPAM removal rate of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 reached 75.3% and 63.59% at optimal conditions. The degraded samples were analyzed with GPC, FTIR, 1H NMR and HPLC. The results showed that HPAM was broken into small fragments, and amide group has been converted into carboxyl group, and no toxic acrylamide monomer was produced. The specific activities of extracellular amidases of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 were 5.31 U/mg and 4.79 U/mg, respectively. This work will provide novel bacteria strains for HPAM-containing wastewater treatment.

Biodegradation and removal of heavy oil using Pseudomonas sp. and Bacillus spp. isolated from oily sludge and wastewater in Xinjiang Oilfield, China

Environmental pollution arising from massive production of oily sludge is a global concern. Microbial remediation is an emerging strategy for cleaning up oily sludge-contaminated sites, but it is still challenging to apply heavy oil-degrading bacteria across regions. The aim of this study was to ascertain the feasibility of biodegrading and removing heavy oil from oily sludge by the use of bacterial strains isolated from oily sludge and wastewater collected from Xinjiang Oilfield, Northwest China. The application potential of these bacterial strains for bioremediation of oily sludge-contaminated soils was also evaluated. A total of six oil-degrading bacteria were isolated, three of which showed excellent oil displacement activity (clear zone diameter: 20–23 cm). The three strains were tentatively identified as Pseudomonas reidholzensis (SB2), Bacillus megaterium (SB4), and B. tequilensis (WB1). In a single-factor experiment, the addition of co-substrates stimulated bacterial growth performance on oily sludge agar plates, and all strains formed the largest colonies (mean diameter >11 mm) with sucrose and glucose as co-substrates. Bacterial treatment led to effective biodegradation of heavy oil extracted from oily sludge within 30 days. When additional carbon source (glucose) and nitrogen source (yeast extract) were used, the degradation rate of extracted heavy oil by SB2, SB4, and WB1 reached 15.60%, 11.95%, and 18.43%, respectively. In the oil samples treated with SB2 and SB4, there was a noticeable decrease in the relative abundances of alkenes, cycloalkanes, isoalkanes, and aromatics, accompanied by a slight increase in the relative abundance of n-alkanes. The major oil components all decreased in WB1-treated oil samples. Under simulated conditions, 13.63%, 9.57% and 15.61% of heavy oil was removed from modified oily sludge by SB2, SB4, and WB1, respectively. The results demonstrate the potential of Pseudomonas sp. and Bacillus spp. as candidate strains for use in oily sludge bioremediation.