-
Biotechnology For Biofuels Dec 2020Converting wastewater sludge to lipid is considered as one of the best strategies of sludge management. The current problem of lipid production from wastewater sludge is...
BACKGROUND
Converting wastewater sludge to lipid is considered as one of the best strategies of sludge management. The current problem of lipid production from wastewater sludge is the low yield (0.10-0.16 g lipid/g dry sludge) due to the low availability of easily uptaken materials (such as soluble monosaccharide and oligosaccharide) in sludge to oleaginous microorganism (Rhodotorula glutinis, Trichosporon oleaginosus, Lipomyces starkeyi). Pretreatments are efficient methods to improve sludge bioavailability. This study is aimed to achieve high lipid production from sludge and high sludge reduction.
RESULTS
In this study, it was observed that the soluble chemical oxygen demand (SCOD) had significantly increased after different pretreatment. The SCOD in the supernatant was increased from 32.64 to 180.25 mg/L, 924.16 mg/L, 1029.89 mg/L and 3708.31 mg/L after acidic (pH 2 for 2 h), alkaline (pH 12 for 2 h), microwave irradiation (15 min with 5 min interval), and ultrasonication (30 min at 450 W and 20 kHz frequency with 5 s on and 2 s off mode) pretreatment, respectively. Pretreatments have also increased the release of total nitrogen (TN) and total phosphorus (TP) from solids. The sludge after different pretreatments were used as a medium for lipid production, and the highest lipid content (36.67% g/g) was obtained in the fermentation with ultrasonication pretreatment sludge, and the sludge reduction was 63.10%. For other pretreatments, the lipid content and sludge reduction were 18.42% and 32.63% in acid pretreatment case, 21.08% and 36.44% in alkaline pretreatment case, and 26.31% and 43.03% in microwave pretreatment case, respectively.
CONCLUSION
It was found that ultrasonication pretreatment was the most efficient way to increase the sludge biodegradability (SCOD) and to release TN and TP from solid phase to liquid phase. Pretreated sludge for lipid production achieved significant improvement in lipid yield and sludge reduction. Lipids produced from pretreated sludge were transesterified to biodiesel and the analysis showed that biodiesel had a similar composition as commercial biodiesel. The study reveals that pretreatment on sludge is a promising method for enhancing biological sludge management efficiency.
PubMed: 33317613
DOI: 10.1186/s13068-020-01844-3 -
Sheng Wu Gong Cheng Xue Bao = Chinese... Nov 2020p-coumaric acid is an important natural phenolic compound with a variety of pharmacological activities, and also a precursor for the biosynthesis of many natural...
p-coumaric acid is an important natural phenolic compound with a variety of pharmacological activities, and also a precursor for the biosynthesis of many natural compounds. It is widely used in foods, cosmetics and medicines. Compared with the chemical synthesis and plant extraction, microbial production of p-coumaric acid has many advantages, such as energy saving and emission reduction. However, the yield of p-coumaric acid by microbial synthesis is too low to meet the requirements of large-scale industrial production. Here, to further improve p-coumaric acid production, the directed evolution of tyrosine ammonia lyase (TAL) encoded by Rhodotorula glutinis tal gene was conducted, and a high-throughput screening method was established to screen the mutant library for improve the property of TAL. A mutant with a doubled TAL catalytic activity was screened from about 10,000 colonies of the mutant library. There were three mutational amino acid sites in this TAL, namely S9Y, A11N, and E518A. It was further verified by a single point saturation mutation. When S9 was mutated to Y, I or N, or A11 was mutated to N, T or Y, the catalytic activity of TAL increased by more than 1-fold. Through combinatorial mutation of three types of mutations at the S9 and A11, the TAL catalytic activity of S9Y/A11N or S9N/A11Y mutants were significantly higher than that of other mutants. Then, the plasmid containing S9N/A11Y mutant was transformed into CP032, a tyrosine-producing E. coli strain. The engineered strain produced 394.2 mg/L p-coumaric acid, which is 2.2-fold higher than that of the control strain, via shake flask fermentation at 48 h. This work provides a new insight for the biosynthesis study of p-coumaric acid.
Topics: Ammonia-Lyases; Coumaric Acids; Escherichia coli; Propionates; Rhodotorula; Tyrosine
PubMed: 33244931
DOI: 10.13345/j.cjb.200122 -
BMC Genomics Nov 2020Rhodotorula glutinis is recognized as a biotechnologically important oleaginous red yeast, which synthesizes numerous meritorious compounds with wide industrial usages....
Genomics and lipidomics analysis of the biotechnologically important oleaginous red yeast Rhodotorula glutinis ZHK provides new insights into its lipid and carotenoid metabolism.
BACKGROUND
Rhodotorula glutinis is recognized as a biotechnologically important oleaginous red yeast, which synthesizes numerous meritorious compounds with wide industrial usages. One of the most notable properties of R. glutinis is the formation of intracellular lipid droplets full of carotenoids. However, the basic genomic features that underlie the biosynthesis of these valuable compounds in R. glutinis have not been fully documented. To reveal the biotechnological potential of R. glutinis, the genomics and lipidomics analysis was performed through the Next-Generation Sequencing and HPLC-MS-based metabolomics technologies.
RESULTS
Here, we firstly assemble the genome of R. glutinis ZHK into 21.8 Mb, containing 30 scaffolds and 6774 predicted genes with a N50 length of 14, 66,672 bp and GC content of 67.8%. Genome completeness assessment (BUSCO alignment: 95.3%) indicated the genome assembly with a high-quality features. According to the functional annotation of the genome, we predicted several key genes involved in lipids and carotenoids metabolism as well as certain industrial enzymes biosynthesis. Comparative genomics results suggested that most of orthologous genes have underwent the strong purifying selection within the five Rhodotorula species, especially genes responsible for carotenoids biosynthesis. Furthermore, a total of 982 lipids were identified using the lipidomics approaches, mainly including triacylglycerols, diacylglyceryltrimethylhomo-ser and phosphatidylethanolamine.
CONCLUSION
Using whole genome shotgun sequencing, we comprehensively analyzed the genome of R. glutinis and predicted several key genes involved in lipids and carotenoids metabolism. By performing comparative genomic analysis, we show that most of the ortholog genes have undergone strong purifying selection within the five Rhodotorula species. Furthermore, we identified 982 lipid species using lipidomic approaches. These results provided valuable resources to further advance biotechnological applications of R .glutinis.
Topics: Biological Products; Carotenoids; Genomics; Lipidomics; Lipids; Rhodotorula
PubMed: 33243144
DOI: 10.1186/s12864-020-07244-z -
Journal of Fungi (Basel, Switzerland) Sep 2020During the course of a screening for novel biologically active secondary metabolites produced by the Sordariomycetes (Ascomycota, Fungi), the ex-type strain of was...
During the course of a screening for novel biologically active secondary metabolites produced by the Sordariomycetes (Ascomycota, Fungi), the ex-type strain of was found to produce seven novel xanthone-anthraquinone heterodimers, xanthoquinodin A11 () and xanthoquinodins B10-15 (-), together with the already known compound xanthoquinodin B4 (). The structures of the xanthoquinodins were determined by analysis of the nuclear magnetic resonance (NMR) spectroscopic and mass spectrometric data. Moreover, the absolute configurations of these metabolites were established by analysis of the H-H coupling constants, nuclear Overhauser effect spectroscopy (NOESY) correlations, and Electronic Circular Dichroism (ECD) spectroscopic data. Antifungal and antibacterial activities as well as cytotoxicity of all compounds were tested. Xanthoquinodin B11 showed fungicidal activities against [minimum inhibitory concentration (MIC) 2.1 µg/mL], (MIC 2.1 µg/mL), and (MIC 8.3 µg/mL). All the compounds - displayed anti-Gram-positive bacteria activity (MIC 0.2-8.3 µg/mL). In addition, all these eight compounds showed cytotoxicity against KB 3.1, L929, A549, SK-OV-3, PC-3, A431, and MCF-7 mammalian cell lines. The six novel compounds (-, -), together with xanthoquinodin B4, were also found in the screening of other strains belonging to , revealing the potential chemotaxonomic significance of the compound class for the genus.
PubMed: 32992954
DOI: 10.3390/jof6040188 -
BMC Microbiology Aug 2020Yeasts, which are ubiquitous in agroecosystems, are known to degrade various xenobiotics. The aim of this study was to analyze the effect of fungicides on the abundance...
BACKGROUND
Yeasts, which are ubiquitous in agroecosystems, are known to degrade various xenobiotics. The aim of this study was to analyze the effect of fungicides on the abundance of natural yeast communities colonizing winter wheat leaves, to evaluate the sensitivity of yeast isolates to fungicides in vivo, and to select yeasts that degrade propiconazole.
RESULTS
Fungicides applied during the growing season generally did not affect the counts of endophytic yeasts colonizing wheat leaves. Propiconazole and a commercial mixture of flusilazole and carbendazim decreased the counts of epiphytic yeasts, but the size of the yeast community was restored after 10 days. Epoxiconazole and a commercial mixture of fluoxastrobin and prothioconazole clearly stimulated epiphyte growth. The predominant species isolated from leaves were Aureobasidium pullulans and Rhodotorula glutinis. In the disk diffusion test, 14 out of 75 yeast isolates were not sensitive to any of the tested fungicides. After 48 h of incubation in an aqueous solution of propiconazole, the Rhodotorula glutinis Rg 55 isolate degraded the fungicide in 75%. Isolates Rh. glutinis Rg 92 and Rg 55 minimized the phytotoxic effects of propiconazole under greenhouse conditions. The first isolate contributed to an increase in the dry matter content of wheat seedlings, whereas the other reduced the severity of chlorosis.
CONCLUSION
Not sensitivity of many yeast colonizing wheat leaves on the fungicides and the potential of isolate Rhodotorula glutinis Rg 55 to degrade of propiconazole was established. Yeast may partially eliminate the ecologically negative effect of fungicides.
Topics: Colony Count, Microbial; Fungicides, Industrial; Microbial Sensitivity Tests; Microbial Viability; Plant Leaves; Triazoles; Triticum; Yeasts
PubMed: 32758148
DOI: 10.1186/s12866-020-01885-6 -
Biotechnology Reports (Amsterdam,... Sep 2020This study focused on the valorization of the date syrup obtained from low-quality date fruits to be used as a low-cost alternative medium for producing single cell oil...
This study focused on the valorization of the date syrup obtained from low-quality date fruits to be used as a low-cost alternative medium for producing single cell oil (SCO) by PTCC5256, which could further be converted into biodiesel. The higher C/N ratio of date syrup (C/N 70) led to restricting the formation of cell biomass and enhancing the biosynthesis of SCO. The maximal cell biomass and lipid productivities were obtained 72 mg/L/h and 17 mg/L/h by C/N ratios of 20 and 70, respectively. Although the obtained biodiesel met the international standards for cold filter plugging point (4.92 °C), iodine value (87.22 g I/100 g oil), cetane number (52.26), higher heating value (40.19 MJ/kg), cloud point (6.29 °C), pour point (0.00 °C), density (878 kg/m), kinematic viscosity (4.30 mm/s) and oxidation stability (7.87 h), its weak cold-flow properties might limit its application in cold areas in comparison with diesel fuel.
PubMed: 32528865
DOI: 10.1016/j.btre.2020.e00480 -
Journal of Food Protection Nov 2020One of the most effective methods for increasing the antimicrobial activity of a substance is to combine it with one or more other antimicrobial agents. The aim of the...
One of the most effective methods for increasing the antimicrobial activity of a substance is to combine it with one or more other antimicrobial agents. The aim of the present study was to evaluate the antimicrobial effect of buforin I and nisin alone and investigate the synergistic action of these compounds against the most important food spoilage microorganisms in clouding B. subtilis, S. epidermidis, L. innocua, E. coli, S. Enteritidis, A. oryzae, R. glutinis and G. candidum. The results of MIC and MBC/MFC examinations showed that buforin I had higher antimicrobial activity than nisin on all the microbial strains used in this study (p≤0.5). E.coli was the most resistant to both antimicrobial agents, while Listeria innocua and Staphylococcus epidermidis were the most sensitive to nisin and buforin I, respectively. The results of synergistic interaction between buforin I and nisin indicated that the combination of buforin I and nisin on B. subtilis, S. epidermidis and A. oryzae showed synergistic effect, while it had no effect on S. Enteritidis and Geotrichum candidum. The combination of buforin I and nisin showed partial synergistic effect on Listeria innocua, Escherichia coli, Rhodotorula glutinis. Assessment of viability of the microorganisms under the antimicrobial agents alone and in combination with each other at MICs and FICs indicated that use of these antimicrobial agents in combination enhances antimicrobial activity at lower concentrations of both agents. The present study investigated the antimicrobial properties of buforin I against food spoilage microorganisms for the first time and suggests that its use alone or in combination with nisin may provide a clear horizon for the application of antimicrobial peptides as natural preservatives. Thus, the combination of antimicrobial peptides and traditional antimicrobial food preservative could be a promising option for the prevention of contamination, spoilage, and infestation of food and beverage products.
PubMed: 32502264
DOI: 10.4315/JFP-20-127 -
MSphere May 2020A small number (10 to 20) of yeast species cause major spoilage in foods. Spoilage yeasts of soft drinks are resistant to preservatives like sorbic acid, and they are...
A small number (10 to 20) of yeast species cause major spoilage in foods. Spoilage yeasts of soft drinks are resistant to preservatives like sorbic acid, and they are highly fermentative, generating large amounts of carbon dioxide gas. Conversely, many yeast species derive energy from respiration only, and most of these are sorbic acid sensitive and so prevented from causing spoilage. This led us to hypothesize that sorbic acid may specifically inhibit respiration. Tests with respirofermentative yeasts showed that sorbic acid was more inhibitory to both and during respiration (of glycerol) than during fermentation (of glucose). The respiration-only species was equally sensitive when growing on either carbon source, suggesting that ability to ferment glucose specifically enables sorbic acid-resistant growth. Sorbic acid inhibited the respiration process more strongly than fermentation. We present a data set supporting a correlation between the level of fermentation and sorbic acid resistance across 191 yeast species. Other weak acids, C to C, inhibited respiration in accordance with their partition coefficients, suggesting that effects on mitochondrial respiration were related to membrane localization rather than cytosolic acidification. Supporting this, we present evidence that sorbic acid causes production of reactive oxygen species, the formation of petite (mitochondrion-defective) cells, and Fe-S cluster defects. This work rationalizes why yeasts that can grow in sorbic acid-preserved foods tend to be fermentative in nature. This may inform more-targeted approaches for tackling these spoilage organisms, particularly as the industry migrates to lower-sugar drinks, which could favor respiration over fermentation in many spoilage yeasts. Spoilage by yeasts and molds is a major contributor to food and drink waste, which undermines food security. Weak acid preservatives like sorbic acid help to stop spoilage, but some yeasts, commonly associated with spoilage, are resistant to sorbic acid. Different yeasts generate energy for growth by the processes of respiration and/or fermentation. Here, we show that sorbic acid targets the process of respiration, so fermenting yeasts are more resistant. Fermentative yeasts are also those usually found in spoilage incidents. This insight helps to explain the spoilage of sorbic acid-preserved foods by yeasts and can inform new strategies for effective control. This is timely as the sugar content of products like soft drinks is being lowered, which may favor respiration over fermentation in key spoilage yeasts.
Topics: Fermentation; Food Microbiology; Food Preservation; Food Preservatives; Sorbic Acid; Yeasts
PubMed: 32461271
DOI: 10.1128/mSphere.00273-20 -
Indian Journal of Microbiology Jun 2020Lipid accumulation is generally believed to be a partially growth-coupled biochemical process that results in differences in lipid content between different cells. To...
Lipid accumulation is generally believed to be a partially growth-coupled biochemical process that results in differences in lipid content between different cells. To separate lipid-rich cells and increase the cellular biomass in bioreactors during the cultivation of the oleaginous yeasts, a gravity sedimentation system (GSS) is coupled to a bioreactor. The dilution rate () and the ratio of the outflow rate from the outlet of the GSS to the inflow rate into the bioreactor () were evaluated. The biomass in the bioreactor with GSS increased by 16.3% and 30.6% at values of 0.05 h (= 0.25) and 0.02 h (= 0.5), respectively. Interestingly, cells containing 39.3% lipids were obtained from the outlet of the GSS ( = 0.02 h, = 0.5), and the lipid content increased by 7.8% compared to that of the bioreactor. The results indicated that use of a GSS is a very effective method for increasing the cell concentration and separation of lipid-rich cells.
PubMed: 32255857
DOI: 10.1007/s12088-019-00849-3 -
ACS Omega Jan 2020Silver nanoparticles (AgNPs) have a large number of applications in technology and physical and biological sciences. These nanomaterials can be synthesized by chemical...
Silver nanoparticles (AgNPs) have a large number of applications in technology and physical and biological sciences. These nanomaterials can be synthesized by chemical and biological methods. The biological synthesis using fungi represents a green approach for nanomaterial production that has the advantage of biocompatibility. This work studies silver nanoparticles (AgNPs) produced by fungi and found in ordinary soil of the Universidade Federal do Ceará campus (Brazil). The biosynthesized AgNPs have a protein-capping layer involving a metallic Ag core. The focus of this paper is to investigate the size and structure of the capping layer, how it interacts with the Ag core, and how sensitive the system (core + protein) is to visible light illumination. For this, we employed SEM, AFM, photoluminescence spectroscopy, SERS, and dark-field spectroscopy. The AgNPs were isolated, and SEM measurements showed the average size diameter between 58 nm for and 30 nm for . These values are in agreement with the AFM measurements, which also provided the average size diameter of 85 nm for and 56 nm for as well as additional information about the average size of the protein-capping layers, whose found values were 24 and 21 nm for and nanoparticles, respectively. The protein-capping layer structure seemed to be easily disturbed, and the SERS spectra were unstable. It was possible to identify Raman peaks that might be related to α-helix, β-sheet, and protein mixed structures. Finally, dark-field microscopy showed that the silver cores are very stable, but some are affected by the laser energy due to heating or melting.
PubMed: 31956786
DOI: 10.1021/acsomega.9b02867