Effect Of Different Carbon Sources Research Articles

Characterization of Thermostable Cellulase Enzyme Isolated from a Hot Spring Bacterium: Bacillus sp.

Cellulase is a complex of enzymes which consists of β-1,4-endoglucanase, cellobiohydrolase, and β-glucosidase. Cellulase contributes a significant share to the world enzyme market and is used in number of industries viz; paper and pulp, food and beverage, bioethanol, detergent and textile. The harsh industrial conditions such as high temperature, extreme pH levels and high substrate concentration etc. which is used in such industries adversely effect on structure and activity of enzymes. Therefore, huge amount of chemical catalysts which cause chemical wastes are used in industrial settings instead of enzymes. Since the chemical wastes adversely affect the ecosystem, isolation and characterization of thermostable cellulase enzyme-producing bacteria and exploring the industrial perspective of thermostable enzymes is a better approach towards green chemistry. The present study focused on characterization of cellulase enzyme produced by Bacillus sp., which shows optimum activity at 60 C under neutral conditions, isolated from Gomarankadavala hot spring in Sri Lanka. The effect of different Carbon sources: glucose and lactose, Nitrogen sources: peptone, tryptone, yeast extract and urea on enzyme production and different Carboxymethylcellulose (CMC) concentrations; 0.5%, 1.5% and 2%, on enzyme activity were measured using the DNS method. Under the optimum conditions, cellulase enzyme activity on different substrates: corn cob, rice bran and raw leaves were measured. The highest enzyme production was recorded in the culture medium which added tryptone as the nitrogen source and adding carbon sources to the culture medium showed an increase of cellulase enzyme production. The optimum CMC concentration for the enzyme activity was recorded as 1% and from all the optimized parameters, the substrate; raw leaves showed the highest enzyme activity of 11.305 U/ml. Further, a considerable amount of enzyme activity was recorded on corn cobs and rice bran as well. Thus, the thermostable cellulase enzyme produced by bacterium identified as Bacillus cereus isolated from Gomarankadavala hot spring could be successfully used in industrial settings such as kitchen/industrial waste management, bioethanol production, paper and pulp industry and textile industry which use high temperatures and cellulosic substrates as raw materials. 
 Keywords: Thermostable enzymes, Cellulase, Industrial applications, Hot springs

The Effect of Different Carbon Sources on Nitrate-Dependent Iron Oxidation Process, Bacterial Diversity, and C Protagonist in Varied Texture Soils

The Effect of Different Carbon Sources on Nitrate-Dependent Iron Oxidation Process, Bacterial Diversity, and C Protagonist in Varied Texture Soils

Application of alkali-heated corncobs enhanced nitrogen removal and microbial diversity in constructed wetlands for treating low C/N ratio wastewater.

Lack of carbon source is the main limiting factor in the denitrification of low C/N ratio wastewater in the constructed wetlands (CWs). Agricultural waste has been considered as a supplementary carbon source but research is still limited. To solve this problem, ferric carbon (Fe-C) + zeolite, Fe-C + gravel, and gravel were used as substrates to build CWs in this experiment, aiming to investigate the effects of different carbon sources (rice straw, corncobs, alkali-heated corncobs) on nitrogen removal performance and microbial community structure in CWs for low C/N wastewater. The results demonstrated that the microbial community and effluent nitrogen concentration of CWs were mainly influenced by the carbon source rather than the substrate. Alkali-heated corncobs significantly enhanced the removal of NO2--N, NH4+-N, NO3-N, and TN. Carbon sources addition increased microbial diversity. Alkali-heated corncobs addition significantly increased the abundance of heterotrophic denitrifying bacteria (Proteobacteria and Bacteroidota). Furthermore, alkali-heated corncobs addition increased the copy number of nirS, nosZ, and nirK genes while greenhouse gas fluxes were lower than common corncobs. In summary, alkali-heated corncobs can be considered as an effective carbon source.

The Effects of Different Carbon Sources on Water Quality, Growth Performance, Hematology, Immune, and Antioxidant Status in Cultured Nile Tilapia with Biofloc Technology

The biofloc technology system (BFT) is considered to be one of the sustainable aquaculture systems, which is based on the principle of nutrient recycling with the addition of a carbon source to give dominance to heterotrophic microorganisms. The objective of this study was to evaluate the effect of sugar cane molasses and tapioca flour as carbon sources on the water quality, growth, hematology, immune status, and non-specific antioxidant status of Oreochromis juveniles. Methodologically, the experiment was carried out for 10 weeks on 225 juvenile Nile tilapia with initial body weights of 47.0 ± 1.3 g that were randomly distributed in 09 tanks (1000 L) with a stocking density of 25 tilapias per tank; the treatments were: BFT + SM (S molasses), BFT + TF tapioca flour (TF), and a control with no carbon source added. The control group was fed 100% feed, while the BFT experimental groups were fed microbial flocs along with 75% feed. The results revealed that the water quality parameters were affected by the carbon sources, but were adequate for normal fish welfare, and the biofloc volume was higher (28.94) with the TF carbon source. The growth performance, such as weight gain (98.61), survival (99.01), and improved feed conversion ratio (FCR) (1.69), was recorded in BFT + TF. Significant improvements in WBCs, HCT, HB, lymphocytes, plasma proteins, albumin, and non-specific immune factors (lysozyme activity, immunoglobulins levels, and ACH50) were observed in biofloc-reared fish with tapioca flour as the carbon source compared to the control and sugarcane molasses groups. Moreover, significant increases in catalase (CAT) and superoxide dismutase (SOD) were found in the biofloc-reared fish with different carbon sources. In conclusion, the use of BFT + TF was found to affect improving the water quality, growth, hematology, immunity, and antioxidant status of juvenile Tilapia.

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.

Evaluation of Lacc134 Oxidoreductase of Ganoderma multistipitatum in Detoxification of Dye Wastewater under Different Nutritional Conditions

In the present study, we investigated the effects of different carbon sources (glucose, sucrose, and maltose) on laccase production from mycelium of Ganoderma multistipitatum grown on malt extract agar plates. The preliminary screening test was performed on the guaiacol plate, where a maroon brown zone formed after laccase oxidation. A few pure mycelial discs of Ganoderma species were transferred into submerged fermentation nutrient broth. The nutrient medium of submerged fermentation at 20 g of glucose revealed the highest laccase activities (2300 U/L) than other carbon sources. The interesting results also shown by inorganic NaNO3 in the production of maximum laccase (7800 ± 1.1 U/L). The organic nitrogen inducer, namely yeast extract, exhibited 5834 U/L laccase activity and a potential source of laccase secretion. The results concluded that C and N inducers enhanced the laccase production. This production process is eco-friendly and effective in the removal of dye from water. Laccase from the cultural broth was partially purified by SDS-PAGE for molecular weight determination, while Native-PAGE confirmed the laccase band after staining with guaiacol. The Km and Vmax values of Lacc134 were 1.658 mm and 2.452 mM min−1, respectively. The Lacc134 of this study effectively removed the Remazol Brilliant Blue R (RBBR) dye (extensively used in textile industries and wastewater). For dye removal capacity, 2.0 mg, 4.0 mg, 5.0 mg, and 6.0 mg were used, from which 6.0 mg was most effective in removal (85% and 88%) dye concentration in 1st and 2nd h interval treatment, respectively. Total organic carbon (TOC) quantity after dye removal percentage in the first- and second-hour time interval was 62% and 89%, respectively, at 30 g glucose. According to the experimental finding of this study, the breakdown products catalyzed by Lacc134 are less hazardous due to lower molecular weight than the dye itself.

Pullulan Production Utilizing Various Carbon Sources by Aureobasidium melanogenum DSM 2404 as Biotherapeutic Tool in Biomedical Applications

Introduction: Pullulan is a biodegradable biopolymer made up of maltotriose subunits that are water-soluble. It has a direct glucan structure comprising α-1,4 and α-1,6 linkages in a 2:1 ratio, which gives it exceptional physical and structural properties, making it a suitable choice for application in biomedical applications. Despite its potential benefits, the price of production is expansive, and productivity is low, which are significant drawbacks. Therefore, the objective of this work is to identify the ideal carbon source for Aureobasidium melanogenum DSM 2404 to produce high pullulans. Methods: In shake flask studies, the effects of different carbon sources, such as maltose, glucose, sucrose, lactose, and xylose, on cell growth and pullulan generation by Aureobasidium melanogenum DSM 2404 were examined. Results: The highest pullulan production was obtained from sucrose (13.38 g L-1) compared to other types of carbon sources used in the fermentation medium. The maximal pullulan production rate of 0.112 [g-1 L-1 h-1] was obtained in sucrose culture. This suggests that sucrose provides favorable conditions for the microorganisms to produce pullulan at a faster rate compared to other sugars. Conclusion: Sucrose was found to be the most efficient carbon source for the synthesis of pullulan using Aureobasidium melanogenum DSM 2404 generating 13.38 g L-1 of pullulan.

The effect of carbon source and temperature on the formation and growth of Bacillus licheniformis and Bacillus cereus biofilms

This study focused on biofilm characteristics of Bacillus licheniformis and Bacillus cereus which were the residual dominant strains in milk powder production system. The effects of different carbon sources (glucose, maltose, lactose and skimmed milk) and temperatures (37 and 55 °C) on biofilm formation and metabolic activity were investigated by crystal violet staining and CCK-8 method. The results showed that the biofilm formation enhanced with the increase of the concentration of carbon source in nutrient broth. The images of the scan electron microscope and light microscope showed that glucose and maltose could significantly increase（p < 0.05） the biomass and metabolic activity of biofilm. Skimmed milk can significantly improve（p < 0.05） the biomass of Bacillus licheniformis and Bacillus cereus biofilm and the metabolic activity of Bacillus licheniformis biofilm. While lactose can only significantly improve （p < 0.05） the metabolic activity of Bacillus licheniformis biofilm, which meant that lactose was not the main component in skimmed milk that affected the biofilm forming ability of Bacillus licheniformis and Bacillus cereus. This study estimated the effect of carbon source and temperature on the formation characteristics of biofilms, and was conductive to the prevention and control of Bacillus pollution in food industry.

Effect of different carbon sources on exopolysaccharide production of Lactiplantibacillus pentosus KS27 and optimization of production conditions using Box-Behnken designing

Effect of different carbon sources on exopolysaccharide production of Lactiplantibacillus pentosus KS27 and optimization of production conditions using Box-Behnken designing

Effects of Different Carbon Sources on Growth and Some Innate Immune Responses of Russian Sturgeon (Acipenser gueldenstaedtii) in Biofloc Systems

The Russian sturgeon (Acipenser gueldenstaedtii) species is in high demand owing to its valuable caviar. Therefore, it is in danger of extinction. Since the Russian sturgeon reaches sexual maturity late in its life cycle, this species has a high economic cost for farmers. However, this high cost can be reduced with an environmentally friendly system called biofloc technology. This study compared the growth performance and health indicators of biofloc groups using different carbon sources such as starch (BS), molasses (BM) and dextrose (BD). In the 60-day study, fish with an average initial weight of 106.44±5.79 g were stocked in tanks at a density of 21 fish/tank (0.4 m3/tank). The water temperature was set at 19 ℃ degrees throughout the study. On the 30th and 60th days of the experiment, fish were weighted to measure the growth parameters and sampled for immune indices. No mortality was observed in any group throughout the study. A between group comparison of weight gain revealed that BS and BM (105.51±2.26; 100.50±2.18) performed better than the control (BC, without external carbon sources) and BD groups (95.90±2.09; 87.36±2.18) (P&amp;lt;0.05). Furthermore, FCR and SGR were calculated from the data obtained at the end of the experiment, and the data shows that the BS and BM groups were statistically more effective than the other groups. Moreover, a comparison of NBT, lysozyme and myeloperoxidase enzyme activities indicated that all BFT groups had a stronger immune system than the control group (P&amp;lt;0.05). According to the results, the immune-enhancing effect of BFT for sturgeon was determined, and it was reported that BS and BM are more suitable for use in this species in terms of FCR and SGR, as they result an economic and environmentally friendly production.

Differences in organic nitrogen transformation during chicken manure composting with the addition of different disaccharides

The effect of different carbon sources on nitrogen (N) transformation and N loss through nitrogenous gas volatilization during composting of manure is not clear. Disaccharides had moderate degradation stability compared to monosaccharides and polysaccharides. Therefore, we investigated the effect of adding sucrose (nonreducing sugar) and maltose (reducing sugar) as carbon sources on volatile N loss and hydrolysable organic nitrogen (HON) transformation. HON is composed of bioavailable organic nitrogen (BON) and hydrolysable unknown nitrogen (HUN). Three laboratory-scale experimental groups were conducted with control (CK), 5 % sucrose (SS), and 5 % maltose (MS) addition. Our findings indicated that, while excluding leaching and surface runoff, adding sucrose and maltose decreased the N loss through gas volatilization by 15.78 % and 9.77 %, respectively. The addition of maltose significantly increased the BON content (P < 0.05), which was 6.35 % higher than in CK. The addition of sucrose led to an increase in HUN content (P < 0.05), which was 22.89 % higher than that in CK. In addition, the core microbial communities associated with HON changed after the addition of disaccharides. The transformation of the HON fractions was facilitated by the succession of microbial communities. Ultimately, variation partition analysis (VPA) and structural equation modeling (SEM) verified that the core microbial communities were the major contributors to promoting HON transformation. In summary, adding disaccharides could promote the different transformations of organic nitrogen (ON) and reduce the volatilization of nitrogenous gases by changing the succession of the core microbial communities during composting. This study provided theoretical and technical support for reducing volatile N loss and promoting ON fraction sequestration during composting. Furthermore, the effect of carbon source addition on the nitrogen cycle was also explored.

Effect of different carbon sources on the conversion of ilmenite into synthetic rutile via ball milling induced carbothermic reduction

Carbothermic reduction reduces ilmenite into TiO2 or acid-soluble intermediates. This method gained more attention due to several industrial applications of TiO2 and metal Ti. However, the efficiency of carbothermic reduction of ilmenite into synthetic rutile is poorly investigated for different carbon sources. In this study, several advanced characterization techniques were used to examine the effect of carbon on the carbothermic reduction of ilmenite via ball milling and isothermal annealing. Fourier transform infrared spectroscopic (FTIR) analysis showed new broad bands appearing in ball milled mixtures (ranging from ∼650 cm−1 to 1200 cm−1), due to temporary bonding of Ti–O–C overlapped with Ti–O–Ti bonding. Scanning electron microscopic (SEM) analysis also suggested that carbon was incorporated in the crystal lattice of ilmenite during ball milling. However, no new phases were observed in the X-ray diffraction (XRD) patterns of ball milled ilmenite-carbon mixtures. Therefore, the energy transferred during ball milling is not sufficient to overcome the activation energy of carbothermic reduction of ilmenite. Phase transformation of ilmenite occurred after annealing at 1000 °C by forming new phases such as rutile, pseudorutile, and pseudobrookite. Intermediate phases such as pseudorutile and pseudobrookite decreased with the use of carbon. Consequently, the efficiency of carbothermic reduction decreased in the order of coconut shells (amorphous)> activated carbon> vein graphite (crystalline). The absence of temporary bonding of Ti–O–C in annealed samples further confirmed the phase transformation of ilmenite. This study also showed that ball milled, and annealed samples resulted in highly crystalline rutile. Thermodynamic behavior of carbothermic reduction was finally simulated using the calculated enthalpy, entropy, and the Gibb’s free energy for each reaction.

Effect of Peganum harmala L. extract supplemented ISP2 medium on growth and production of secondary metabolites of Streptomyces ayarius S115

BackgroundThe present work aimed to investigate the effect of Peganum harmala L. in increasing the growth and production of secondary metabolites of Streptomyces ayarius strain S115 via ISP2 culture medium. Peganum harmala L. was dried and added to ISP2 medium. The morphological properties and the antibacterial activity of S. ayarius strain S115 seeded in ISP2 and the modified ISP2 media was evaluated by using the agar well diffusion method against five pathogenic bacteria, Escherichia coli Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia sp. and Methicillin-Resistant Staphylococcus aureus. The biomass of S. ayarius strain S115 in both media was determined. The kinetics of growth and production of secondary metabolites were studied for 7 d in different carbon sources. ResultsCulture on the modified ISP2 showed an effective growth of S. ayarius strain S115 with changed color of the aerial mycelium from gray to white. The antibacterial activity revealed large inhibition zones against the tested pathogenic bacteria compared to those of the ISP2. The amount of S. ayarius strain S115 biomass was twice as high in the modified ISP2. The effect of different carbon sources on the growth and production of secondary metabolites of S. ayarius strain S115 revealed the highest biomass and biological activities through using glucose in the modified ISP2 on the 3rd day of culture. Of note, glycerol was found as the optimal carbon source in ISP2. ConclusionsThe discovery of new bioactive molecules from actinomycetes seeded in specific culture media may contribute to the development of therapeutic solutionsHow to cite: Nait Marzoug A, Ayari A, Khaldi F, et al. Effect of Peganum harmala L. extract supplemented ISP2 medium on growth and production of secondary metabolites of Streptomyces ayarius S115. Electron J Biotechnol 2023;64. https://doi.org/10.1016/j.ejbt.2022.12.006.

Effects of carbon sources on phosphorus speciation transformation process, characteristics of extracellular polymeric substances, and microecology in anaerobic systems

The effects of different carbon sources on the transformation process of the form of phosphorus and microecology were examined in an anaerobic system using glucose and L-malic acid as carbon sources. Results showed that for these two carbon sources (glucose and L-malic acid), the average removal efficiencies of chemical oxygen demand by up-flow anaerobic sludge bed reactors were 97.16 % and 88.63 %, and the average removal efficiencies of total phosphorus were 11.38 % and 5.68 %, respectively. The average concentrations of phosphine in anaerobic reactors using glucose and L-malic acid as carbon sources were 160.73 mg/m3 and 90.80 mg/m3 over days 24–40, respectively. When glucose was used as carbon source, the proportions of biologically available phosphorus (i.e., the sum of non-apatite inorganic phosphorus and organic phosphorus content) within total phosphorus in sludge on days 0, 20, and 40 were 76.22 %, 77.90 %, and 85.04 %, respectively. Glucose could better promote the enhancement of dehydrogenase activity than L-malic acid. The carbon source affected the activity of alkaline phosphatase, and the enzyme activity was stronger when glucose was used as carbon source. Kyoto Encyclopedia of Genes and Genomes functional analysis showed that amino acid metabolism and carbohydrate metabolism dominated. On days 0, 30 and 60, the relative abundances of carbohydrate metabolism in microorganisms using glucose as carbon source were 0.26 %, 0.36 %, and 0.34 % higher than those with L-malic acid as carbon source, respectively.

Modulation of gut flore by dietary fibers from Pyrus bretschneideri Rehd.: Evaluation of fermentation characteristics using a colonic in vitro fermentation model

Nutrients such as dietary fiber in Pyrus bretschneideri Rehd. (PBR), which is mainly produced on the Tibetan Plateau, can be used as a fermentable carbon source for microorganisms. However, the mechanisms by which different carbon sources interact with microorganisms and their fermentation metabolites are not clear. In this study, four different carbon sources extracted from PBR were used to explore the effect of carbon source type on gut flora (GF) and the metabolites thereof through an in vitro simulated colonic fermentation model. The results showed a differentiation of the type of carbon source on the species composition and structure of GF, as well as on the production of metabolites during in vitro fermentation. Correlations between some microbial taxa and their metabolites were also revealed, such as Subdoligranulum and acetic acid, Collinsella and propionic acid, and Fusicatenibacter and butyric acid showing significant positive correlations. Notably, a cross-feeding pathway was clarified: Anaerostipes uses lactic acid and acetic acid as substrates to produce butyric acid. Overall, this study provided insight into the effects of different carbon sources from PBR as fermentation substrates on GF growth and metabolism, which could provide a basis for exploring the relationship between carbon source types, GF and their metabolites, and promote the integrated development of PBR resources in Qinghai Province.

Effect of different carbon sources on callus formation, pigment accumulation, and antiviral activity in cell cultures of Euphorbia milii

Effect of different carbon sources on callus formation, pigment accumulation, and antiviral activity in cell cultures of Euphorbia milii

Effect of different carbon sources on sulfate reduction and microbial community structure in bioelectrochemical systems.

Microbial electrolysis cells (MECs) have rapidly developed into a promising technology to treat sulfate-rich wastewater that lacks electron donors. Hence, a better understanding of the effect on the microbial community structure caused by different sources in bioelectrochemical systems is required. This study sought to investigate the effect of different carbon sources (NaHCO3, ethanol, and acetate were employed as sole carbon source respectively) on the performance of sulfate-reducing biocathodes. The sulfate reduction efficiency enhanced by the bioelectrochemical systems was 8.09 - 11.57% higher than that of open-circuit reference experiments. Furthermore, the optimum carbon source was ethanol with a maximum sulfate reduction rate of 170mg L-1 d-1 in the bioelectrochemical systems. The different carbon sources induced significant differences in sulfate reduction efficiency as demonstrated by the application of a micro-electrical field. Microbial community structure and network analysis revealed that all three kinds of carbon source systems enriched large proportions of sulfate-reducing bacteria and electroactive bacteria but were significantly distinct in composition. The dominant sulfate-reducing bacteria that use NaHCO3 and acetate as carbon sources were Desulfobacter and Desulfobulbus, whereas those that use ethanol as carbon source were Desulfomicrobium and Desulfovibrio. Our results suggest that ethanol is a more suitable carbon source for sulfate reduction in bioelectrochemical systems.

Effects of different carbon sources on water quality, biofloc quality, and the productivity of Nile tilapia reared in biofloc-based ponds

Abstract The present study evaluated the effects of different carbohydrates materials used as carbon sources on water quality, biofloc quality, and growth and productive performance of Nile tilapia (Oreochromis niloticus) reared in biofloc (BFT)-based cement ponds (25 m x 10 m x 1.2 m; with 250 m3 volume). Nile tilapia fingerlings (44.9±1.9 g) were distributed into nine ponds at a density of 40 fish per 1 m3 (10000 fish/pond) to represent three treatments in triplicates. The control ponds received no carbon source addition; meanwhile sugarcane molasses (MO) and wheat flour (WF) were added to ponds. A commercial diet (30% crude protein) was offered to fish in each pond at levels of 3% and 2% of live body weight of fish in the control and BFT-based ponds, respectively, for 12 weeks. The amounts of feed were divided equally to three equal portions and offered to fish at 9:00, 13:00, and 17:00 h. The control ponds’ water was replaced by 50% every day with new water; meanwhile in MO and WF ponds, water loss via evaporation or leakage was compensated to reach the 1.0 m depth only. The pH value as well as unionized ammonia and nitrite levels, in the present study, were significantly lower, meanwhile nitrate and total suspended solids levels were significantly higher in MO and WF-treated ponds than the control one. The WF treatment resulted in significantly larger biofloc volume and higher total bacterial count compared to the MO treatment. The highest growth and production indices of Nile tilapia were observed in the BFT-based treatments as compared with the control group; particularly at the WF treatment followed by the MO treatment. In conclusion, the WF addition to cement fishponds is a more beneficial carbonaceous source for the efficient water quality, biofloc biomass, and growth and productivity of Nile tilapia reared in BFT-based system.

The effect of different carbon sources on biofouling in membrane fouling simulators: microbial community and implications

Biofouling is a problem affecting the operation of nanofiltration systems due to the complexity of the carbon matrix affecting bacteria and biofilm growth. This study used membrane fouling simulators to investigate the effects of five different carbon sources on the biofouling of nanofiltration membranes. For all the carbon sources analyzed, the increase in pressure drop was most accelerated for acetate. The use of acetate as the single carbon source produced less adenosine triphosphate but more extracellular polymers than glucose. The microbial community was analyzed using 16 s rRNA. The use of more than a single carbon source produced an increase in bacteria diversity even at similar concentrations. The relative abundance of proteobacteria was the highest at the phylum level (95%) when a single carbon source was added. Additionally, it was found that the use of different carbon sources produced a shift in the microbial community, affecting the biofouling and pressure drop on membranes.

Effects of different carbon sources on the oxidative stress tolerance of Aspergillus niger HY2 isolated from spoiled paddies.

Fungi often experience oxidative stress in response to the environment during growth. In this study, Aspergillus niger HY2, whose presence easily results in paddy mildew, was used to investigate the effects of different carbon sources on morphological development, reactive oxygen species (ROS) metabolites, and antioxidant enzymes activities. Morphological development mainly includes the changes in conidial production and colony diameter. ROS metabolites production include the content of hydrogen peroxide (H2O2), superoxide anion (O2·-), and malondialdehyde (MDA). The results indicated that A. niger HY2 adapted to H2O2 exposure by decreasing growth and increasing the activities of some antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Different carbon sources also affected the expression of the developmental-specific gene flbA and the oxidative stress tolerance-related gene cat. When incubated with glucose, sucrose, and xylose as carbon sources, A. niger exhibited stronger oxidative stress tolerance, but when incubated with maltose as a carbon source, A. niger exhibited relatively poor oxidative stress tolerance. Our results can provide a theoretical basis for further understanding mechanisms of metabolic adaptation and developing targeted strategies to control the spoilage caused by A. niger.