Medium Components Research Articles

Validation of the volumetric flow cytometry for bovine sperm concentration

Sperm concentration is a stronghold of the andrological evaluation and the production of insemination doses. The use of haemocytometers, although considered the gold standard, is difficult to apply in field conditions because it is subjective and time-consuming. The present study was designed to validate the volumetric flow cytometry (volFC) in order to estimate bovine sperm concentration, comparing it with the performances of haemocytometer, NucleoCounter, and flow cytometry with the use of fluorospheres. Compared with other methods, volFC appeared less affected by large dilution of the sample, with similar concentrations calculated in the range of dilution 1:200–1:800. Using volFc the population detected on the basis of morphological criteria and fluorescence of DNA better represents the real concentration of sperm in the sample. The volFC showed high repeatability compared with the haemocytometer (coefficient of variation 1.85% and 4.52%, respectively) and stable performances with cryopreserved samples, with negligible effects of the medium components. The present study showed that volFC is as accurate and precise as other techniques to estimate sperm concentration in bovine fresh and frozen semen, but it is less affected by operative conditions, such as sample dilution. The possibility to quantify sperm functional subpopulations by volFC could potentially implement the study of the relationship between sperm attributes and fertility.

Influence of the interstellar magnetic field and 11-year cycle of solar activity on the heliopause nose location

Context. The heliosphere is formed by the interaction between the solar wind (SW) plasma emanating from the Sun and a magnetised component of local interstellar medium (LISM) inflowing on the Sun. A separation surface called the heliopause (HP) forms between the SW and the LISM. Aims. In this article, we define the nose of the HP and investigate the variations in its location. These result from a dependence on the intensity and direction of the interstellar magnetic field (ISMF), which is still not well known but has a significant impact on the movement of the HP nose, as we try to demonstrate in this paper. Methods. We used a parametric study method based on numerical simulations of various forms of the heliosphere using a time-dependent three-dimensional magnetohydrodynamic (3D MHD) model of the heliosphere. Results. The results confirm that the nose of the HP is always in a direction that is perpendicular to the maximum ISMF intensity directly behind the HP. The displacement of the HP nose depends on the direction and intensity of the ISMF, with the structure of the heliosphere and the shape of the HP depending on the 11-year cycle of solar activity. Conclusions. In the context of the planned space mission to send the Interstellar Probe (IP) to a distance of 1000 AU from the Sun, our study may shed light on the question as to which direction the IP should be sent. Further research is needed that introduces elements such as current sheet, reconnection, cosmic rays, instability, or turbulence into the models.

Comparison of Peat–Perlite-based and Peat–Biochar-based Substrates with Varying Rates of Calcium Silicate on Growth and Cannabinoid Production of Cannabis sativa ‘BaOx’

Growers have been searching for alternative horticultural growing media components because of their desire to use sustainable resources. Biochar is a carbon-based material that has been evaluated for use as an alternative aggregate in peat-based soilless substrates. Additionally, silicon (Si) has been examined as a beneficial element to promote plant growth and plant quality in a variety of crops. However, there has been limited research regarding the interaction of biochar as an aggregate and Si in soilless substrates. This study aimed to determine the impact of Si and biochar on plant growth and nutrient uptake for greenhouse-cultivated hemp (Cannabis sativa L.). Hemp plants were grown in one of 12 different substrate blends: with two rates of calcium silicate (CaSiO3), two aggregate types of biochar (medium or coarse) or perlite, and aggregate percentages of 85% peat + 15% aggregate and 70% peat + 30% aggregate. The cannabinoid concentration, plant height, diameter, or total plant biomass were similar across all substrate blends after 12 weeks of growth. Additionally, the use of CaSiO3 as a Si substrate amendment increased Si foliar concentrations, and the addition of biochar to peat-based mixes did not limit the Si availability for plant uptake. However, Si substrate amendments did not impact plant height, diameter, or total plant biomass. This suggests that the biochar tested during this study is suitable in peat-based substrates for C. sativa ‘BaOx’ production at rates up to 30% (by volume) in peat-based substrates with CaSiO3 amendments.

Genomic insights into antimicrobial potential and optimization of fermentation conditions of pig-derived Bacillus subtilis BS21.

Bacillus spp. have been widely used as probiotic supplements in animal feed as alternatives to antibiotics. In the present study, we screened a Bacillus subtilis strain named BS21 from pig feces. Antimicrobial activities, whole genome mining and UHPLC-MS/MS analysis were used to explore its antimicrobial mechanism. Strain BS21 showed Significant growth inhibition against a variety of animal pathogens, including Escherichia coli, Salmonella enterica Pullorum, Salmonella enterica Typhimurium, Citrobacter rodentium, Shigella flexneri and Staphylococcus aureus. Seven gene clusters involved in antimicrobial biosynthesis of secondary metabolites were encoded by strain BS21 genome, including four non-ribosomal peptides (bacillibactin, fengycin, surfactin and zwittermicin A), one ribosomal peptide (subtilosin A), one dipeptide (bacilysin) and one polyketide (bacillaene). Among them, production of surfactin, fengycin, bacillibactin, bacilysin and bacillaene was detected in the supernatant of B. subtilis strain BS21. To develop the potential application of BS21 in animal production, medium components and fermentation parameters optimization was carried out using response surface methodology (RSM). Production of antimicrobial secondary metabolites of strain BS21 was increased by 43.4%, and the best medium formula after optimization was corn flour 2%, soybean meal 1.7% and NaCl 0.5% with optimum culture parameters of initial pH 7.0, temperature 30°C, rotating speed at 220 rpm for 26 h. Our results suggested that strain BS21 has the potential for large-scale production and application as a potential source of probiotics and alternative to antibiotics for animal production.

Heat Transfer Enhancement of Energy Pile with Nanofluids as Heat Carrier

As one of the core components of the transport medium in the energy pile system, the circulating working fluid is crucial for the enhancement of its heat transfer efficiency. In this study, based on the heat transfer enhancement theory of nanofluids, deionized water was used as the base solution to prepare the corresponding 0, 0.5, 1, and 1.5 vol% nanofluids by introducing nanoparticles SiO2, Al2O3, CuO, and Cu. The laws of thermal conductivity and specific heat capacity with the volume fraction of different nanofluids are studied by the comparison. The results of thermal conductivity research illustrate that the specific heat capacity of nanofluids decreases linearly with the increase of the volume concentration of nanoparticles, but the thermal conductivity increases linearly. The fluid with the highest thermal conductivity and specific heat capacity is Cu–water nanofluids. In addition, it is proposed to directly apply all kinds of nanofluids with 1 vol% as circulating fluid to self-made miniature model box of energy pile to simulate the working conditions in summer. The influence laws of the nanofluids on the flow rate and heat transfer efficiency in the energy pile were calculated through the temperature difference between the inlet and outlet of the heat exchange tube. The results reveal that the nanofluids used in the experiment exert a optimization influence on the heat transfer of energy pile but the mass flow rate of the nanofluids during the circulation is decreased compared with that of the deionized water circulation liquid. Among them, the temperature difference between inlet and outlet of Cu–water nanofluid is the largest, which has the best effect on improving the heat transfer efficiency of the energy pile but its mass flow loss is also the largest. The research results can provide a reliable reference for the improvement of heat transfer efficiency of energy pile engineering in the future.

Bioremediation of an industrial soil contaminated by hydrocarbons in microcosm system, involving bioprocesses utilizing co-products and agro-industrial wastes.

The present study describes practical implication of bioaugmentation and biostimulation processes for bioremediation of an industrial soil chronically contaminated by hydrocarbons. For this purpose, biomass production of six autochthonous hydrocarbon-degrading bacteria were evaluated as inoculum of bioaugmentation strategy, by testing carbon and nitrogen sources included co-products and agro-industrial waste as sustainable and low-cost components of the growth medium. Otherwise, biostimulation was approached by the addition of optimized concentration of nitrogen and phosphorus. Microcosm assays showed that total hydrocarbons (TH) were significantly removed from chronically contaminated soil undergoing bioremediation treatment. Systems Mix (bioaugmentation); N,P (biostimulation) and Mix + N,P (bioaugmentation and biostimulation) reached higher TH removal, being 89.85%, 91.00%, 93.04%, respectively, comparing to 77.83% of system C (natural attenuation) at 90days. The increased heterotrophic aerobic bacteria and hydrocarbon degrading bacteria counts were according to TH biodegrading process during the experiments. Our results showed that biostimulation with nutrients represent a valuable alternative tool to treat a chronically hydrocarbon-contaminated industrial soil, while bioaugmentation with a consortium of hydrocarbon degrading bacteria would be justified when the soil has a low amount of endogenous degrading microorganisms. Furthermore, the production of inoculum for application in bioaugmentation using low-cost substrates, such as industrial waste, would lead to the development of an environmentally friendly and attractive process in terms of cost-benefit.

Prehistoric human activities and environmental background during the Late Neolithic to Bronze period in the Minjiang River Basin, Southeast China, based on luminescence ages and chemical elemental analysis of pottery

The Minjiang River Basin in Fujian played a vital role in the southward spread of agriculture in China. To better understand the development of Neolithic cultures in this region and the interactions between the people of Southeast China and their environment, as well as the formation and development of agricultural civilizations in East Asia, this study focused on determining the luminescence ages of nine pottery/burnt clay samples and measuring 33 trace elements in 38 pottery/burnt clay and 15 sediment samples collected from the Minjiang River Basin. The reliability of determining luminescence age using heated quartz was also investigated. By combining the characteristics of trace elements with the background of prehistoric human environments, this study aimed to explore the relationships between humans and the environment and cultural interactions during the late Neolithic period in the Minjiang River Basin. The results showed that some pottery samples displayed a higher proportion of medium and slow components in their initial quartz optically stimulated luminescence (OSL) signals, but most OSL ages were not affected. The ages of the pottery samples were concentrated during stable environmental periods characterized by relatively high sea levels, elevated surface sea temperatures, and low El Niño–Southern Oscillation occurrence frequencies. The chemical composition and principal component analysis suggested that the majority of pottery samples were locally sourced, while pottery from coastal islands may have originated from upstream areas of the Minjiang River. This indicates that there was cultural exchange in the Minjiang River Basin during the Neolithic culture period, rather than being limited to the local living. Differences in subsistence patterns could serve as a driving force behind cross-regional cultural exchanges, which likely deepened over time.

Synthesis of silver nanoparticles using Bacillus velezensis M3-7 lipopeptides: Enhanced antifungal activity and potential use as a biocontrol agent against Fusarium crown rot disease of wheat seedlings

Bacillus velezensis M3-7 is a hyperactive mutant, 12-fold improved in its antifungal activity, obtained during a previous study from the wild strain BLB371 after a combination of random mutagenesis and medium component optimization. This study explores the use of this mutant in synthesizing silver nanoparticles (Ag-NPs) for the control of Fusarium crown rot disease (FCR) in wheat seedlings. LC-MS/MS analysis proved that both strains co-produced different families of lipopeptides and that mutagenesis caused the hyper-production of iturin A C14 and C15, the liberation of iturin A C10 and C12, and the inhibition of fengycin release. Our aim was a further improvement in the antifungal activity of the wild strain and the mutant M3-7 in order to control Fusarium crown rot disease (FCR) in wheat seedlings. Therefore, a nanotechnology approach was adopted, and different lipopeptide concentrations produced by the wild strain and the mutant M3-7 were used as capping agents to synthesize silver nanoparticles (Ag-NPs) with enhanced antifungal activity. Ag-NPs formed using 3 mg·mL−1 of the mutant lipopeptides were found to exhibit a good distribution, improved antifungal activity, a promising potential to be used as a biofortified agent for seed germination, and an effective compound to control FCR in wheat seedlings.

Application of Optimization Models in Modification of Nutrient- Chloramphenicol Agar Medium for Use in Selective Isolation of Pseudomonasfluorescens.

Commercially available medium for selective isolation of Pseudomonas are relatively expensive. Incorporation of chloramphenicol into nutrient agarhas been used in the selective isolation of Pseudomonasfluorescens. Theaim of this study was to apply optimization in modification of nutrient-chloramphenicol agar medium (NCAM) so as to optimize it for selective isolation of Pseudomonas species. Water sample determined to contain fluorescent greenish-pigment producing bacteria (FGPB) was used for the optimization study. Medium component selected for the optimization process were pH, NaCl concentration (NC), and chloramphenicol concentration (CC), with value ranges of 7.0 – 8.2, 0.5 – 1.0 %, and 40 – 60 ?g/ml, respectively. Fifteen media variations were derived from combination of these ranges using Box-Behnken design matrix,and were used in culturing the water sample for isolation of FGPB. Relationship between obtained proportions of bacterial populations that are FGPB and chosen media components were calculated using polynomial equation for three factors design. Prediction profiles derived from the equation showed that the highest proportion of bacterial populations that are FGPB was achievable at pH, NC, and CC combination values of 7.0, 0.2 %, and 60 ?g/ml, respectively. NCAM with this optimized combination increased the efficiency of selectively isolating FGPB from the water samplefrom 0.008 to 0.011 %. Physicochemical/biochemical testing showed that the FGPBisolates were Pseudomonas fluorescens. It is concluded that NCAM with pH 7.0, NaCl concentration of 0.2 %, and chloramphenicol concentration of 60 ?g/ml can be used for selective isolation of Pseudomonas fluorescens with optimum efficiency.

THE ROLE OF SOCIAL MEDIA MARKETING ON BRAND AWARENESS AND STUDENT DECISIONS TO CHOOSE UNIVERSITY

This study is aimed to analyze the influence of social media marketing activities on brand awareness and students' decisions in choosing higher education institutions. The population in this study was students of Universitas Duta Bangsa, data collection methods using online questionnaires, and data analysis methods using SEM-PLS. The results of this study found that marketing activities through social media have a positive effect on the decision to choose a university. The components of social media marketing activities that influence the decision to choose a university are entertainment, interactivity, trendy, customization, and E-WOM. Meanwhile, what affects brand awareness is entertainment, customization, and E-WOM.

Enhancing the growth of thermophilic Bacillus licheniformis YYC4 by low-intensity fixed-frequency continuous ultrasound

The effect of low-intensity fixed-frequency continuous ultrasound (LIFFCU) on the growth of Bacillus licheniformis YYC4 was investigated. The changes in morphology and activity of the organism, contributing to the growth were also explored. Compared with the control, a significant increase (48.95%) in the biomass of B. licheniformis YYC4 (at the logarithmic metaphase) was observed following the LIFFCU (28 kHz, 1.5 h and 120 W (equivalent to power density of 40 W/L)) treatment. SEM images showed that ultrasonication caused sonoporation, resulting in increased membrane permeability, evidenced by increase in cellular membrane potential, electrical conductivity of the culture, extracellular protein and nucleic acid, and intracellular Ca2+ content. Furthermore, LIFFCU action remarkably increased the extracellular protease activity, volatile components of the culture medium, microbial metabolic activity, and spore germination of the strain. Therefore, LIFFCU could be used to efficiently promote the growth of targeted microorganisms.

Improvement of Rice Blast Resistance in TGMS Line HD9802S through Optimized Anther Culture and Molecular Marker-Assisted Selection.

Rice blast caused by Magnaporthe oryzae is one of the most serious rice diseases worldwide. The early indica rice thermosensitive genic male sterile (TGMS) line HD9802S has the characteristics of stable fertility, reproducibility, a high outcrossing rate, excellent rice quality, and strong combining ability. However, this line exhibits poor blast resistance and is highly susceptible to leaf and neck blasts. In this study, backcross introduction, molecular marker-assisted selection, gene chipping, anther culture, and resistance identification in the field were used to introduce the broad-spectrum blast-resistance gene R6 into HD9802S to improve its rice blast resistance. Six induction media were prepared by varying the content of each component in the culture medium. Murashige and Skoog's medium with 3 mg/L 2,4-dichlorophenoxyacetic acid, 2 mg/L 1-naphthaleneacetic acid, and 1 mg/L kinetin and N6 medium with 800 mg/L casein hydrolysate, 600 mg/L proline, and 500 mg/L glutamine could improve the callus induction rate and have a higher green seedling rate and a lower white seedling rate. Compared to HD9802S, two doubled haploid lines containing R6 with stable fertility showed significantly enhanced resistance to rice blast and no significant difference in spikelet number per panicle, 1000-grain weight, or grain shape. Our findings highlight a rapid and effective method for improving rice blast resistance in TGMS lines.

A foundational approach to culture and analyze malnourished organoids

ABSTRACT The gastrointestinal (GI) epithelium plays a major role in nutrient absorption, barrier formation, and innate immunity. The development of organoid-based methodology has significantly impacted the study of the GI epithelium, particularly in the fields of mucosal biology, immunity, and host-microbe interactions. Various effects on the GI epithelium, such as genetics and nutrition, impact patients and alter disease states. Thus, incorporating these effects into organoid-based models will facilitate a better understanding of disease progression and offer opportunities to evaluate therapeutic candidates. One condition that has a significant effect on the GI epithelium is malnutrition, and studying the mechanistic impacts of malnutrition would enhance our understanding of several pathologies. Therefore, the goal of this study was to begin to develop methodology to generate viable malnourished organoids with accessible techniques and resources that can be used for a wide array of mechanistic studies. By selectively limiting distinct macronutrient components of organoid media, we were able to successfully culture and evaluate malnourished organoids. Genetic and protein-based analyses were used to validate the approach and confirm the presence of known biomarkers of malnutrition. Additionally, as proof-of-concept, we utilized malnourished organoid-derived monolayers to evaluate the effect of malnourishment on barrier formation and the ability of the bacterial pathogen Shigella flexneri to infect the GI epithelium. This work serves as the basis for new and exciting techniques to alter the nutritional state of organoids and investigate the related impacts on the GI epithelium.

Phytohormones regulate asexual Toxoplasma gondii replication.

The protozoan Toxoplasma gondii (T. gondii) is a zoonotic disease agent causing systemic infection in warm-blooded intermediate hosts including humans. Duringthe acute infection, the parasite infects host cells and multiplies intracellularly in the asexual tachyzoite stage. In this stage of the life cycle, invasion, multiplication, and egress are themost critical events in parasite replication. T. gondii features diverse cell organelles to support these processes, including the apicoplast, an endosymbiont-derived vestigial plastid originating from an alga ancestor. Previous studies have highlighted that phytohormones can modify the calcium-mediated secretion, e.g., of adhesins involved in parasite movement and cell invasion processes. The present study aimed to elucidate the influence of different plant hormones on the replication of asexual tachyzoites in a human foreskin fibroblast (HFF) host cell culture. T. gondii replication was measured by the determination of T. gondii DNA copies via qPCR. Three selected phytohormones, namely abscisic acid (ABA), gibberellic acid (GIBB), and kinetin (KIN) as representatives of different plant hormone groups were tested. Moreover, the influence of typical cell culture media components on the phytohormone effects was assessed. Our results indicate that ABA is able to induce a significant increase of T. gondii DNA copies in atypical supplemented cell culture medium when applied in concentrations of 20 ng/μl or 2 ng/μl, respectively. In contrast, depending on the culture medium composition, GIBB may potentially serve as T. gondii growth inhibitor and may be further investigated as a potential treatment for toxoplasmosis.

Vectorial EM Propagation Governed by the 3D Stochastic Maxwell Vector Wave Equation in Stratified Layers

The modeling and processing of vectorial electromagnetic (EM) waves in inhomogeneous media are important problems in physics and engineering, and new methods need to be developed to incorporate novel vector sensor technology. Vectorial phenomena of EM waves in stratified atmospheric layers can be incorporated into governing equations by retaining the gradient of the refractive index when deriving the Maxwell Vector Wave Equation (MVWE) from Maxwell’s equations. The MVWE, as opposed to the scalar wave, Helmholtz, and paraxial equations, couples the EM field components in inhomogeneous media and thus captures important physics phenomena such as depolarization. Here, recent developments are reviewed on using sensor time series data to reconstruct electromagnetic waves that propagate through stratified media. In modern applications, often many sensors can be deployed simultaneously to observe electromagnetic waves. These networks of sensors can be used to improve the quality of the reconstructed EM wave fields and cross-validate the observed sensor time series. Lastly, the effects of noisy current densities on sensor time series are considered. Generally, as the sensor observes for longer periods of time, the variance of estimates of the wave field obtained from sensor time series data increases. As a result, longer sensor observation times do not always result in better estimates of the EM wave fields, and an optimal observation time can be obtained.

Bioleaching of ion-adsorption rare earth ores by biogenic lixiviants derived from agriculture waste via a cell-free cascade enzymatic process

Biogenic organic acids are considered environmentally friendly alternatives to ammonium sulfate for leaching ion-adsorption rare earth ores. Fermentation is popular for their production, but undesired cell metabolites and residual medium components could dampen the leaching performance. High feedstock cost is another major barrier for their applications. To tackle these challenges, a cell-free cascade enzymatic process was developed to produce gluconate from low-cost rice straw. Gluconate production by fermentation and enzymatic catalysis was first compared, and it was found that the enzymatic process gave a 99% yield within 24 h, while it was only 60% for fermentation after 48 h. The gluconate from enzymatic process was superior to that from fermentation in terms of leaching efficiency (100% vs. 18.1%). The precipitation of rare earth elements (REEs) by residual phosphate was identified as the major contributor to the low leaching performance by gluconate produced via fermentation. The gluconate derived from rice straw via the cascade enzymatic process did not show a compromised leaching efficiency, reaching 100% as well. This study sheds lights on how enzymatic process could be adopted to circumvent interferences for REEs recovery by fermentative impurities, and opens a new avenue for potentially economical production of biogenic lixiviants from renewable and cheap feedstocks.

Application of Azolla spp. as a Growing Medium Component for Melon Grown in a Soilless Culture System

Azolla spp. is a prominent macrophyte and one of the world’s fastest growing plants, making it a highly important resource that has been widely exploited as a biofertilizer, food and feed, and biofuel production. As a result, the uses, promotion, and application of Azolla spp. in sustainable agriculture would be of significant interest. The objectives of this study were (i) to assess the feasibility of using Azolla as a growing media of melons with a reduction in fertigation concentration in a soilless culture system, and (ii) to compare the agronomic and fruit quality traits of melons grown in different Azolla treatments. The experiment was carried out using a completely randomized design with 4 treatments including: (1) control treatment (1:1 combination of chopped coconut mesocarp (CCM) and coconut coir (CC) with recommended fertigation concentration (RFC)), (2) dried Azolla (1:1:2 combination of CCM, CC, and dried Azolla with 75% of RFC), (3) fermented Azolla (1:1:2 combination of CCM, CC, and fermented Azolla with 75% of RFC), and (4) fresh Azolla (1:1:2 combination of CCM, CC, and fresh Azolla with 75% of RFC). Seven melons per treatment were recorded on the agronomic traits (stem length, stem diameter, leaf width, leaf length, and leaf number) and fruit quality (fruit weight, fruit height, fruit perimeter, rind thickness, pulp thickness, fruit cavity, pulp firmness, pulp color (L*, a*, b*, Hue, and c*), total soluble solid, juice electrical conductivity, juice pH, and juice titratable acidity). Statistical analyses revealed the differences among melon agronomic and yield traits under different Azolla treatments. Nutrient analysis results showed that fermented and fresh Azolla had a high nutritional value as compared to dried Azolla. Most fruit traits from fermented and fresh Azolla treatments with a fertilizer reduction were not significantly different as compared to control. Both treatments were recommended for melon production in a soilless culture system, since these treatments can reduce fertigation use by 25% while maintaining growth and fruit quality when compared to conventional practice.

Optimization of medium and media components for maximum biomass of Halobacterium salinarum NRC-1 using Response Surface Methodology

Often, biotechnological advances are hindered by low growth rate of microorganisms utilized in the process, making optimal design of culture media a crucial aspect to consider in the biotechnology field. Materials and Method: Optimization of media components for growth and biomass production of Halobacterium salinarum NRC-1, our organism of interest, was carried out using response surface methodology, a statistical approach to optimize and improve the performance of a process by analyzing the relationships between input variables and output responses. A linear model was estimated and media components were determined based on the linear regression equation generated by the model. The variables chosen were casein enzyme hydrolysate, yeast extract, arginine, and peptone. Results & Discussion: An optimum result for the four variables was predicted based on the experimental response, which is 7.5 g/L of casein enzyme hydrolysate and yeast extract each, and 5.0 g/L each of peptone and arginine. The optimized medium reduced the time required for the cell culture to attain stationary phase, and showed a significant increase in the amount of biomass obtained as compared with that in standard media.

A novel approach to modify Stenotrophomonas sp. D6 by regulating the salt composition in the growth medium: Enhanced removal performance of Cr(VI)

In this study, a novel and effective modified microbial reducing agent was developed to detoxify Cr(VI) from aqueous solutions. This was achieved by carefully controlling specific salt components in the growth medium. Based on the single-salt modification, several effective modified salts were selected and added to the medium for synergistic modification. The results showed that the synergistic modification with NH4Cl and KH2PO4 had the best detoxification effect on Cr(VI), reaching 98.5% at 100 mg/L Cr(VI), which was much higher than the 43.7% of the control (original Luria-Bertani medium). This enhancement was ascribed to the ability of NH4Cl and KH2PO4 to stimulate the growth of Stenotrophomonas sp. D6 promoted chromate reductase secretion. The protein content of the modified medium supernatant was significantly increased by 10.76% compared to that before modification. Based on the micro-characterization, the main process for the elimination of Cr(VI) is microbial reduction rather than biosorption. Most of the reduced Cr was found in the extracellular suspension, thereby suggesting that the primary reduction occurred outside the cells, whereas only a small fraction was detected intracellularly. Overall, this study provides a simple and effective method for microbial treatment of heavy metals in aqueous solutions.

Optimization of Molasses and Soybean Meal Content to Enhance Tetramethylpyrazine Yield by Bacillus sp. TTMP20.

Microbial fermentation for the production of tetramethylpyrazine (TTMP) is considered to be the most promising method, and the development of a cheap fermentation substrate is of great importance for large-scale TTMP production. In this study, inexpensive by-products from the food industry, i.e., molasses and soybean meal (instead of glucose and tryptone), were used as substrates for TTMP fermentation. The pretreatment of soybean meal was explored in order to achieve a better fermentation effect. The contents of each component in the fermentation medium were optimized by central composite design (CCD). The optimum contents were as follows: 72.5 g/L of molasses, 37.4 g/L of diammonium hydrogen phosphate (DAP), 53.4 g/L of soybean meal, and 5 g/L of yeast powder. The software predicted a maximum TTMP yield of 1469.03 mg/L, and the actual TTMP yield was 1328.95 mg/L for the validation experiment in the optimum medium. Under the optimum conditions (72.5 g/L of molasses, 37.4 g/L of DAP, 53.4 g/L of soybean meal, and 5 g/L of yeast powder), the actual maximum TTMP yield (1328.95 mg/L) in this study was much higher than the TTMP yield (895.13 mg/L) under the conditions (150 g/L of molasses, 30 g/L of DAP, 30 g/L of tryptone, and 10 g/L of yeast powder) of our previous study published in Molecules. In this study, the TTMP yield improved by 48.46%, with decreased molasses (more than half), decreased yeast powder (half) and by-product soybean meal instead of tryptone compared to our previous study. In summary, the cheaper fermentation medium had a higher TTMP yield in this study, which improves the application potential of Bacillus sp. TTMP20.