Microorganisms are indispensable in the food industry, but wild-type strains hardly meet the current industrial demands due to several undesirable traits. Therefore, microbial strain improvement ...offers a critical solution to enhance the food industry. Traditional techniques for food microbial improvement, such as the use of chemical mutagens and manual isolation/purification, are inefficient, time-consuming, and laborious, restricting further progress in the area of food fermentation. In this review, the applications of novel mutagenesis and screening technologies used for the improvement of food microbes were summarized, including random mutagenesis based on physical irradiation, microbial screening facilitated by a microtiter plate, fluorescence-activated cell or droplet sorting, and microscaled fermentation in a microtiter plate or microbioreactor. In comparison with conventional methods, these new tools have the potential in accelerating microbial strain improvement and their combined applications could create a new trend for strain development. However, several problems that could affect its potential application may include the following: the lack of specific mutagenesis devices and biosensing systems, the insufficient improvement of the mixed culture system, the low efficiency when using filamentous fungi and flocculating bacteria, and the insufficient safety assessment on harnessing genome-editing technology. Therefore, future works on strain improvement remain challenging for the food industry.
Calcium-rich biochars (CRB) prepared through pyrolysis of crab shell at various temperatures were characterized for physicochemical properties and P removal potential. Elemental analysis showed that ...CRB was rich in calcium (22.91%–36.14%), while poor in carbon (25.21%–9.08%). FTIR, XRD and TG analyses showed that calcite-based CRB was prepared at temperature ≤600 °C, while lime-based CRB was prepared at temperature ≥700 °C. Phosphorus removal experiment showed that P removal efficiencies in 80 mg P/L phosphate solution and biogas effluent ranged from 26% to 11%, respectively, to about 100% and 63%, respectively, depending on the pyrolysis temperature of the resulting biochar. Specifically, compared to common used CaCO3 and Ca(OH)2, P removal potential of calcite-based CRB was much higher than that of CaCO3; while that of lime-based CRB was close to that of Ca(OH)2. These results suggested that CRB was competent for P removal/recovery from wastewater.
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•Calcium-rich biochar (CRB) for phosphorus removal was prepared from crab shell.•Calcite-based CRB was prepared at temperature ≤600 °C.•Lime-based CRB was prepared at temperature ≥700 °C.•Calcite-based CRB showed higher phosphorus removal potential than CaCO3.•Phosphorus removal potential of lime-based CRB was close to that of Ca(OH)2.
The surplus of manure phosphorus (P) with increasing livestock production might pose a risk of P loss to the environment due to the high mobility of P in manure. Thus, there is an increasing need to ...mitigate P loss from manure. This study aimed to investigate the effect of hydrothermal carbonization (HTC) on the immobilization of P in cow manure. The results demonstrated that the P content in cow manure was increased substantially by ∼20% after HTC, while the water-extractable P (WEP) and Mehlich-3-extractable P (MEP) in manure was reduced significantly by >80% and 50%, respectively. The decrease in P solubility might result from the increased apatite P (increased by >85%) and decreased soluble Ca (decreased by ∼50%) after HTC. These results suggested that HTC could be an efficient strategy to immobilize P in cow manure, thereby potentially mitigating the P loss problem from cow manure.
•Cow manure (85% moisture) was directly treated by hydrothermal carbonization (HTC).•The water extractable phosphorus (P) in manure was reduced by >80% during HTC.•The Mehlich-3 extractable P in manure was reduced by >50% during HTC.•The decreased P mobility was attributed to the formation of apatite P during HTC.
Biorefinery of biomass-based biofuels and biochemicals by microorganisms is a competitive alternative of traditional petroleum refineries. Zymomonas mobilis is a natural ethanologen with many ...desirable characteristics, which makes it an ideal industrial microbial biocatalyst for commercial production of desirable bioproducts through metabolic engineering. In this review, we summarize the metabolic engineering progress achieved in Z. mobilis to expand its substrate and product ranges as well as to enhance its robustness against stressful conditions such as inhibitory compounds within the lignocellulosic hydrolysates and slurries. We also discuss a few metabolic engineering strategies that can be applied in Z. mobilis to further develop it as a robust workhorse for economic lignocellulosic bioproducts. In addition, we briefly review the progress of metabolic engineering in Z. mobilis related to the classical synthetic biology cycle of “Design-Build-Test-Learn”, as well as the progress and potential to develop Z. mobilis as a model chassis for biorefinery practices in the synthetic biology era.
•Z. mobilis has attractive features for lignocellulosic biofuels and biochemicals.•Progress achieved for expanded substrate utilization and robustness improvement.•Knowledge learned from Z. mobilis can be employed in other microorganisms.•Z. mobilis can be developed as a synthetic chassis.
Furfural is a major inhibitor in lignocellulose hydrolysate for
Zymomonas mobilis
. A mutant F211 strain with high furfural tolerance was obtained from our previous study. Thus, its key tolerance ...mechanism was studied in the present study. The function of mutated genes in F211 was identified by functional complementation experiments, revealing that the improved furfural tolerance was resulted from the C493T mutation of the ZCP4_0270 gene promoting cell flocculation and the mutation (G1075A)/downregulation of ZCP4_0970. Comparative transcriptome analysis revealed 139 differentially expressed genes between F211 and the control, CP4, in response to furfural stress. In addition, the reliability of the RNA-Seq data was also confirmed. The potential tolerance mechanism was further demonstrated by functional identification of tolerance genes as follows: (I) some upregulated or downregulated genes increase the levels of NAD(P)H, which is involved in the reduction of furfural to less toxic furfuryl alcohol, thus accelerating the detoxification of furfural; (II) the mutated ZCP4_0270 and upregulated cellulose synthetase gene (ZCP4_0241 and ZCP4_0242) increased flocculation to resist furfural stress; (III) upregulated molecular chaperone genes promote protein synthesis and repair stress-damaged proteins; and (IV) transporter genes ZCP4_1623–1,625 and ZCP4_1702–1703 were downregulated, saving energy for cell growth. The furfural-tolerant mechanism and corresponding functional genes were revealed, which provides a theoretical basis for developing robust chassis strains for synthetic biology efforts.
•Lanthanum doped hydrochar was prepared by one-pot hydrothermal carbonization.•The adsorbents was highly effective in P adsorption in a wide range of pH.•The competing anions showed little negative ...effects on P adsorption on the adsorbent.
Engineered hydrochar composites (EHC) were synthesized by hydrothermal carbonization (HTC) of lanthanum pretreated rice straw. The as-prepared composite with about 30% lanthanum content showed greater P removal potential than La(OH)3, indicating the synergistic effect of hydrochar and lanthanum in P removal. The adsorption results showed that EHC showed great P adsorption capacities (>50mgPg−1) in the pH range of 2.5–10.5, and the presence of competing anions had little negative effects on P adsorption on EHC. The equilibrium time for P adsorption on EHC was considerably reduced under acid condition (12h) compared to alkaline condition (48h). The maximum adsorption capacity was 61.57mgPg−1 according to Langmuir isotherms. These results suggested that EHC was highly effective in P adsorption in a wide range of pH and the presence of competing anions, thus EHC could be a promising adsorbent for phosphorus removal/recovery from wastewater.
A Gram-staining-positive, spore-forming, strictly anaerobic bacterium, designated strain LAM0A37T, was isolated from enrichment samples collected from a petroleum reservoir in Shengli oilfield. Cells ...of strain LAM0A37T were rod-shaped and motile by peritrichous flagella. The optimal temperature and pH for growth were 40 °C and 7.0–7.5, respectively. The strain did not require NaCl for growth but tolerated up to 3 % (w/v) NaCl. Strain LAM0A37T was able to utilize glucose, fructose, maltose, xylose, sorbitol, cellobiose, melibiose and melezitose as sole carbon sources. Sulfite was used as an electron acceptor. The main products of glucose fermentation were acetate and CO2. The predominant fatty acid was C16 : 0 (23.6 %). The main polar lipid profile comprised of five glycolipids, six phospholipids and two lipids. No menaquinone was detected. The genomic DNA G+C content was 27.1 ± 0.2 mol% as determined by the T m method. Analysis of the 16S rRNA gene sequence indicated that the isolate was a member of the genus Terrisporobacter, and was most closely related to Terrisporobacter glycolicus JCM 1401T and Terrisporobacter mayombei DSM 6539T with 98.3 % 16S rRNA gene sequence similarity to both. DNA–DNA hybridization values between strain LAM0A37T and type strains of Terrisporobacter glycolicus and Terrisporobacter mayombei were 45.6 ± 0.3 % and 38.3 ± 0.4 %, respectively. Based on phenotypic, phylogenetic and chemotaxonomic characteristics, strain LAM0A37T is suggested to represent a novel species of the genus Terrisporobacter, for which the name Terrisporobacter petrolearius sp. nov. is proposed. The type strain is LAM0A37T ( = ACCC 00740T = JCM 19845T).
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•A LAB SynCom was constructed to abate NH3 emissions from livestock manure.•The LAB SynCom showed high lactic acid productivity and adaptability to manure.•A total of 95.5% of pig ...manure ammonia emissions were reduced by the novel strategy.•The lactic acid bacteria community reshaped manure microbial community structure.•Manure ureolytic bacteria were notably inhibited under the novel mitigation strategy.
The global livestock system is one of the largest sources of ammonia emissions and there is an urgent need for ammonia mitigation. Here, we designed and constructed a novel strategy to abate ammonia emissions via livestock manure acidification based on a synthetic lactic acid bacteria community (LAB SynCom). The LAB SynCom possessed a wide carbon source spectrum and pH profile, high adaptability to the manure environment, and a high capability of generating lactic acid. The mitigation strategy was optimized based on the test and performance by adjusting the LAB SynCom inoculation ratio and the adding frequency of carbon source, which contributed to a total ammonia reduction efficiency of 95.5 %. Furthermore, 16S rDNA amplicon sequencing analysis revealed that the LAB SynCom treatment reshaped the manure microbial community structure. Importantly, 22 manure ureolytic microbial genera and urea hydrolysis were notably inhibited by the LAB SynCom treatment during the treatment process. These findings provide new insight into manure acidification that the conversion from ammonia to ammonium ions and the inhibition of ureolytic bacteria exerted a synergistic effect on ammonia mitigation. This work systematically developed a novel strategy to mitigate ammonia emissions from livestock waste, which is a crucial step forward from traditional manure acidification to novel and environmental-friendly acidification.
The production of biofuels and biochemicals derived from microbial fermentation has received a lot of attention and interest in light of concerns about the depletion of fossil fuel resources and ...climatic degeneration. However, the economic viability of feedstocks for biological conversion remains a barrier, urging researchers to develop renewable and sustainable low-cost carbon sources for future bioindustries. Owing to the numerous advantages, acetate has been regarded as a promising feedstock targeting the production of acetyl-CoA-derived chemicals. This review aims to highlight the potential of acetate as a building block in industrial biotechnology for the production of bio-based chemicals with metabolic engineering. Different alternative approaches and routes comprised of lignocellulosic biomass, waste streams, and C1 gas for acetate generation are briefly described and evaluated. Then, a thorough explanation of the metabolic pathway for biotechnological acetate conversion, cellular transport, and toxin tolerance is described. Particularly, current developments in metabolic engineering of the manufacture of biochemicals from acetate are summarized in detail, with various microbial cell factories and strategies proposed to improve acetate assimilation and enhance product formation. Challenges and future development for acetate generation and assimilation as well as chemicals production from acetate is eventually shown. This review provides an overview of the current status of acetate utilization and proves the great potential of acetate with metabolic engineering in industrial biotechnology.
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