Amino acids in yeast fermentation: A review of their roles from nutrients to modulators.

To address the issues of resistance and environmental pollution caused by over-reliance on chemical pesticides in the control of Botrytis cinerea, this study aimed to isolate efficient biocontrol bacteria from unique habitats for the development of new resources for green control. Antagonistic strains were isolated from facility agriculture soil on the Qinghai-Tibet Plateau. Their taxonomic status was determined through morphological, physiological, biochemical, and comprehensive molecular identification based on 16S rDNA and gyrB gene sequences. The antifungal activity and biocontrol potential were evaluated using plate confrontation assays, in vitro fruit protection tests, and microscopic observation. Moreover, culture conditions including carbon source, nitrogen source, temperature, salinity, and pH were systematically optimized. A highly effective biocontrol strain, HZ-61, was isolated and identified as Bacillus pumilus. This strain exhibited an inhibition rate of 75% against B. cinerea in plate assays and achieved a control efficacy of 94.12% in detached fruit tests. It also induced extensive hyphal fragmentation and deformation in the pathogen. Optimization of culture conditions revealed that the optimal carbon source was yeast extract, the optimal nitrogen sources were peptone or tryptone, the optimal growth temperature was 28°C, the optimal salinity was 1% NaCl, and the optimal pH was 7.0. Strain HZ-61 demonstrated remarkable antifungal activity and biocontrol potential against B. cinerea, providing a preliminary theoretical basis and a key microbial resource for the development of efficient and environmentally friendly microbial agents.

Mycelium-based leather-like material from Absidia koreana grown on agro-residues: Process optimisation, functionalisation, and material performance

Genetic characterization and mutagenesis of fat-degrading enzymes from Bacillus cereus for enhanced lipid degradation and esterification.

Sulfadiazine degrading bacteria Vibrio alginolyticus isolated from mariculture wastewater: Performance, degradation pathways, and mechanisms based on transcriptomic analysis.

A novel bacterium with heterotrophic nitrification-aerobic denitrification (HN-AD) capability, designated Pseudomonas sp. L5, was isolated from the activated sludge of an aerobic denitrification reactor in our laboratory and subsequently identified. This strain can efficiently conduct nitrogen metabolism using NH4 +-N, NO3 --N and NO2 --N as nitrogen sources. Single-factor experiments combined with response surface methodology (RSM) were used to optimize the culture conditions of strain L5. The predicted optimal conditions for growth and nitrogen removal were a C/N ratio of 31.29, sodium acetate as the carbon source, a temperature of 31.18°C, and an initial pH of 7.25. Notably, even under mildly alkaline conditions (pH 9.0), the strain maintained high aerobic denitrification efficiency, with a NO3 --N removal rate of 86.236%. The nitrogen metabolism pathway of strain L5 was elucidated through a combined analysis of the expression of key HN-AD genes and enzyme activities. The denitrification capacity of strain L5 under alkaline conditions provides a theoretical basis and technical support for the application of aerobic denitrifying bacteria in high-pH wastewater treatment.

Development and validation of a novel DTNB-based assay for tryptophanase activity: A tool for research applications.

Chitin-rich organic wastes in aquatic environments provide ecological niches for chitinolytic microorganisms capable of converting chitin into chitosan, a high-value biopolymer with applications in agriculture, biotechnology, and environmental management. Microbial chitosan production represents a sustainable alternative to conventional chemical extraction; however, its efficiency is strongly influenced by environmental and physicochemical process parameters. This study investigated the occurrence, chitinolytic potential, and chitosan-producing capacity of indigenous microorganisms isolated from freshwater and sediment samples in Minna, Niger State, Nigeria, and optimised production under controlled fermentation conditions. Physicochemical characteristics of water bodies were determined, followed by the isolation and characterisation of bacterial and fungal chitinolytic strains. Selected isolates were screened for chitinase activity and subjected to fermentation-based chitosan production. Process optimisation was performed using a five-factor central composite design to assess the effects of temperature, pH, glucose level (5-20g L⁻¹), nitrogen source concentration (1-5g L⁻¹), and incubation time, with response surface methodology applied for model development and interaction analysis. Low dissolved oxygen and moderate temperatures favoured chitinolytic genera, including Aspergillus, Bacillus, and Fusarium, with Aspergillus niger exhibiting the highest chitosan yield. Incubation time was the most significant factor (p < 0.001), while temperature, pH, and substrate concentration showed strong interaction effects. Initial batch fermentations yielded up to 0.20g L⁻¹ chitosan from selected isolates, while response surface optimisation with Aspergillus niger increased production to 1.46g L⁻¹ at 32.8°C, pH 5.12, 15.3g L⁻¹ glucose, 2.45g L⁻¹ yeast extract, and 5.2 days incubation. The optimised product exhibited a high degree of deacetylation, indicating suitability for agricultural and environmental applications. These findings highlight inland aquatic ecosystems as valuable reservoirs of chitinolytic microorganisms and provide an optimised, environmentally benign framework for scalable microbial chitosan production.

Metabolic and genetic basis of heterotrophic nitrification and aerobic denitrification coupled with phosphorus removal by Comamonas testosteroni ZSJS.

Ammonium-regulated high-cell-density heterotrophic cultivation enhances cost-effective chrysolaminarin production in Poterioochromonas malhamensis.

Distinct interaction between management history and nitrogen source drive microbial nitrogen processes in soil

Ammonium is the preferred nitrogen source for microorganisms. We investigated the regulation of ammonium transporters Amt1, Amt2 and Amt3 in the fission yeast Schizosaccharomyces pombe. Expression of the amt1+ gene increases under nitrogen starvation as well as in the TORC1-deficient mutant tor2-287, suggesting negative regulation of amt1+ by TORC1. This regulation depends on the GATA transcription factor Gaf1, the phosphorylation of which is regulated by Ppe1 and PP2A phosphatases. Ppe1 is required for the nuclear accumulation of Gaf1, partly contributing to the controlled expression of amt1+. In contrast, PP2A phosphatase is essential for amt1+ induction upon starvation, indicating distinct roles for Ppe1 and PP2A in Gaf1 regulation. Nitrogen starvation also promotes the plasma membrane translocation of Amt1 and Amt2 in a manner dependent on the Tsc-Rhb1 pathway. Intriguingly, the amt1Δ amt2Δ tscΔ mutant is more sensitive to low-ammonium conditions than the amt1Δ amt2Δ amt3Δ triple mutant. Thus, there might be an unidentified ammonium transporter that is also dependent on the Tsc-Rhb1 pathway for its plasma membrane localization.

One-step microwave-assisted synthesis of nitrogen-doped carbon quantum dots for highly sensitive and selective fluorescence detection of mercury (II) ion in food.

A Bacillus sp. isolated from a saltern soil was shown to produce a blend of extracellular enzymes including amylase, cellulase, inulinase, and pectinase. Different carbon substrates (citrus peels, potato peels) were tested for enzyme production. Maximum activities of all enzymes were obtained in a 72-h aerobic batch culture at pH 6 and 45°C, but on different substrates. The best nitrogen source for producing the enzymes was corn steep liquor (CSL) among six possible sources tested. Use of a mixed carbon source of untreated lignocellulosic biomass (total concentration = 30g L-1; 12.5:12.5:5 (by mass) mixture of lemon peel, orange peel, and potato peel) in combination with CSL (5g L-1) maximized production of all the enzymes. All enzymes were stable at 50°C for up to 24h. The cell-free crude enzyme mixture was shown to effectively saccharify (24-h batch operation at 50°C, pH 6) several lignocellulosic substrates (rice straw, potato peel, or a mixture of these) that had been pretreated with the ionic liquid 1-butyl-3-methylimidazolium chloride. Saccharification of potato peel was enhanced in the presence of polyethylene glycol (3g L-1). The glucose released during saccharification could be directly fermented in a subsequent step to ethanol. Ethanol yields of up to 70% (by mass) of the theoretically possible yield were achieved on available glucose.

Optimized physio-chemical conditions for improved xylanase production by Streptomyces sp. CSMPJR101 isolated from bamboo forest soil.

Consolidated bioprocessing (CBP) by cellulolytic fungi offers a direct route for cellulosic ethanol production, but the process still relies heavily on costly complex nitrogen sources. Replacing complex nitrogen with inorganic nitrogen is a potential strategy to reduce the cost of the medium, yet it often leads to impaired fermentation performance, and the metabolic basis for this limitation remains unclear. Replacement of yeast extract with inorganic nitrogen was evaluated in the engineered thermophilic fungus Myceliophthora thermophila YL913, a CBP strain capable of producing ethanol directly from cellulose. Ammonium sulfate supported higher ethanol production than nitrate, but still resulted in a lower titer than yeast extract. Under ammonium sulfate, transcriptomic and metabolomic analyses revealed altered amino acid metabolism together with reduced carbohydrate metabolic and cellulose catabolic functions, while supplementation with selected amino acids provided only limited improvement. Supplementation with 5 mg/L thiamine pyrophosphate (TPP) increased ethanol production under ammonium sulfate from 14.3 g/L to 23 g/L, reaching a level comparable to that obtained with yeast extract. Moreover, α-ketoglutarate was identified as a responsive metabolic node associated with the altered fermentation state. Stepwise strengthening of the endogenous TPP biosynthetic pathway progressively improved ammonium-based ethanol fermentation, and additional overexpression of pyruvate decarboxylase further enhanced ethanol production. In a 5-L fermenter, the final engineered strain produced 49.5 g/L ethanol under ammonium sulfate without exogenous TPP, close to the 51.2 g/L obtained with the TPP-supplemented parental strain. This study establishes ammonium sulfate as a feasible low-cost alternative to yeast extract for CBP-based cellulosic ethanol production by the engineered M. thermophila strain. These findings provide a practical strategy for developing low-cost fungal CBP processes for cellulosic ethanol production supported by inorganic nitrogen.

Free fatty acids are considered a potential source of biodiesel because they are excreted by engineered cyanobacterial cells, eliminating the processing costs associated with cell recovery and extraction. Although the cyanobacterial mutants engineered for the production of free fatty acids do excrete significant amounts of the product, the yield per dry cell weight is low due to their rapid proliferation and the consequent substantial cell biomass, which makes it impossible to support sustainable biofuel production. Development of strategies to increase the production of free fatty acids per cell is urgently needed. To increase the per-cell production of free fatty acids, we attempted to increase the allocation of photosynthetically fixed carbon into fatty acid production by restricting cell proliferation. Growth limitation of free fatty acid-producing cells was achieved by cultivating dAS2T, a free fatty acid-producing mutant of Synechococcus elongatus PCC 7942 defective in active nitrate uptake, in media containing nitrate as the sole source of nitrogen. Although the nitrogen-limited cultivation increased the per-cell yield of free fatty acids, it significantly decreased the extracellular free fatty acid level, reducing the volumetric productivity. Overexpressing an endogenous free fatty acid-efflux pump in the dAS2T strain elevated extracellular free fatty acid level to those seen under nitrate-sufficient conditions, while maintaining slow cell growth. By decoupling the production of fatty acids from cell growth in this manner, excretion of 0.90 g of free fatty acids per g of dry cell weight was achieved in 240 h, with a free fatty acid productivity of 1.8 mg L-1 h-1. This represents the highest yield of free fatty acids obtained to date without significantly decreasing the volumetric productivity. Growth limitation and enhancement of excretion of the product are essential to increase the per-cell yield of the free fatty acid production system using cyanobacteria. The high yield and productivity of extracellular free fatty acids achieved in this study suggest that the cyanobacteria-based production of free fatty acids provides a reliable approach for sustainable biofuel production through the "milking" strategy.

We developed N-doped carbon quantum dots (N-CQDs) as both photocathode modifiers and electrolytes for self-powered portable photoelectrochemical (PEC) cells to generate electricity under visible-light illumination. Using betaine-type Meldonium precursor, and either ethylenediamine, N,N-dimethylformamide or NH3·H2O as a nitrogen source deliver three different N-CQDs featuring both surface-negatively-charged and positively-charged groups. Due to structural-directing template functionality of ethylenediamine, N-CQDs(en) incorporates the highest pyridinic-N content, which facilitates the charge conductivity and fine-regulates the reaction selectivity within Csp2-frameworks. As semiconductor-coatings electrodeposited on Cu2O, N-CQDs(en) integrate with Cu2O into heterojunctions (N-CQDs(en)/Cu2O) to improve charge separation and promote 4e- oxygen-reduction into water. Importantly, encapsulating an aqueous solution containing N-CQDs(en) in a gelatin/sodium L-pyroglutamate-derived conductor gives a quasi-solid-state electrolyte that facilitates the charge migration, improving the electrodes-electrolytes interfacial incompatibility, while also possibly helping to in situ complement active sites on the modified photocathode. Coupled with a FeNiOOH/FeN-decorated BiVO4 photoanode, enabling the efficient 4e- water oxidation, the complete system establishes a self-sustaining H2O-O2-H2O cycle. The resulting PEC cell shows impressive electricity output for over 120h under irradiation, enough to power some small electronics. Unlike conventional photovoltaics, this cell is moisture-tolerant, oxidation-resistant and concurrently harnesses light and chemical energy, presenting a new paradigm for next-generation light-to-electricity conversion.

Methylated amines (MAs) are ubiquitous in the marine environment, constituting an important part of the marine dissolved organic nitrogen pool and contributing to the formation of cloud condensation nuclei in the marine atmosphere. The aerobic trimethylamine (TMA) oxidation pathway represents the primary route for TMA utilization in marine environments and has been characterized in the model marine Roseobacter group bacterium Ruegeria pomeroyi DSS-3. However, the regulatory mechanism underlying this pathway has remained unclear. Transcriptome analysis revealed coordinated induction of the entire pathway by all intermediate MAs. We identified a master regulator, TmaR, which is essential for the growth of R. pomeroyi DSS-3 on any MA. TmaR functions as an activator of tdm and its downstream enzymatic genes, and as a mild repressor of tmm. It regulates target gene transcription by directly binding to their promoter regions and responds to further catabolite(s) derived from MMA. Another regulator, TmoR, acts as a strong repressor of tmm by binding to its promoter. The tmaR gene is widely distributed among alpha- and gamma-proteobacteria, and in most cases, it is located within MA catabolic gene clusters. Together, these results identify a master regulator of TMA catabolism in globally abundant marine bacteria.IMPORTANCETrimethylamine (TMA) is a key marine nitrogen source; however, its catabolic regulation remains poorly understood. This study identifies TmaR as the master transcriptional regulator of the TMA catabolic pathway in abundant marine bacteria. TmaR is essential for growth on all methylated amines, directly activating downstream genes' transcription while repressing the initial tmm gene, and responds to downstream MMA catabolite(s). This coordinated regulation enables efficient nitrogen acquisition from mixed methylamine substrates, a common marine scenario. Homologs of TmaR are widespread among marine Alpha- and Gammaproteobacteria, indicating a conserved regulatory strategy for a globally significant biogeochemical process. Our findings provide crucial molecular insight into ocean nitrogen cycling.

Heterologous nitrate transporter enhance lipid accumulation in Yarrowia lipolytica through coordinated regulation of lipid metabolism