http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Metabolic Engineered Pseudomonas putida Strain for Propionic Acid Production
Rameshwar TIWARI,Sung Kuk LEE 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Propionic acid is an industrially relevant organic acid used in various applications like food, agricultural, and pharmaceutical industries. However, petrochemical based unsustainable propionic acid production leads to the development of microbial bioprocess from renewable substrates like lignocellulosic biomass. Levulinic acid is a γ-keto acid (C5) platform chemical produced by acid-catalyzed dehydration and the hydrolysis of sugars obtained from lignocellulosic biomass without using expensive hydrolytic enzymes. The metabolic pathway of levulinic acid utilization was discovered in Pseudomonas putida strain and further used for levulinic acid-based biorefinery to produce biologically diverse chemicals. Moreover, P. putida is recognized as a safe microbial host and is emerging as a next-generation industrial workhorse due to its metabolic versatility and remarkable tolerance to oxidative stress, organic solvents, and aromatic compounds. In present work, levulinic acid assimilation pathway of P. putida EM42 strain was directed to produce propionic acid by blocking side pathways and its interconversion into propionyl-CoA. Further, levulinic acid-inducible expression system was used to express metabolic genes for propionic acid production. Metabolic engineered P. putida strain was used to optimize the bioprocess for higher production yield of propionic acid. This study revealed the exploitation of levulinic acid catabolic pathway from P. putida as an alternative route for the sustainable and industrial production of propionic acid.
( Snigdha Tiwari ),( Rameshwar Avchar ),( Riya Arora ),( Vikram Lanjekar ),( Prashant K. Dhakephalkar ),( Sumit S. Dagar ),( Abhishek Baghela ) 한국균학회 2020 Mycobiology Vol.48 No.6
Xylophagous termites are capable of degrading lignocellulose by symbiotic gut microorganisms along with the host’s indigenous enzymes. Therefore, the termite gut might be a potential niche to obtain natural yeasts with celluloytic, xylanolytic and ethanologenic traits required for bioethanol production from lignocellulosic biomass. In this study, we cultured 79 yeasts from three different termites viz. Coptotermes heimi, Odontotermes javanicus and Odontotermes obesus. After suitable screening methods, we identified 53 yeasts, which belonged to 10 genera and 16 different species of both ascomycetous and basidiomycetous yeasts. Most yeasts in the present study represent their first-ever isolation from the termite gut. Representative strains of identified yeasts were evaluated for their cellulolytic, xylanolytic, and ethanologenic abilities. None of the isolates showed cellulase activity; 22 showed xylanolytic activity, while six produced substantial quantities of ethanol. Among xylanolytic cultures, Pseudozyma hubeiensis STAG 1.7 and Hannaella pagnoccae STAG 1.14 produced 1.31 and 1.17 IU of xylanase. Among ethanologenic yeasts, the strains belonging to genera Candida and Kodamaea produced high amount of ethanol. Overall, highest ethanol level of 4.42 g/L was produced by Candida tropicalis TS32 using 1% glucose, which increased up to 22.92 g/L at 35 ℃, pH 4.5 with 5% glucose. Fermentation of rice straw hydrolysate gave 8.95 g/l of ethanol with a yield of 0.42 g/g using the strain TS32. Our study highlights the gut of wood-feeding termites as a potential source of diverse yeasts that would be useful in the production of xylanase and bioethanol.
( Sangeeta Pandey ),( Rameshwar Tiwari ),( Surender Singh ),( Lata Nain ),( Anil Kumar Saxena ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.8
A total of 10 cellulase-producing bacteria were isolated from soil samples irrigated with paper and pulp mill effluents. The sequencing of 16S rRNA gene revealed that all isolates belonged to different species of genus Bacillus. Among the different isolates, B. subtilis IARI-SP-1 exhibited a high degree of β-1,4-endoglucanase (2.5 IU/ml), β-1,4-exoglucanase (0.8 IU/ml), and β-glucosidase (0.084 IU/ml) activity, followed by B. amyloliquefaciens IARI-SP-2. CMC was found to be the best carbon source for production of endo/exoglucanase and β-glucosidase. The β-1,4-endoglucanase gene was amplified from all isolates and their deduced amino acid sequences belonged to glycosyl hydrolase family 5. Among the domains of different isolates, the catalytic domains exhibited the highest homology of 93.7%, whereas the regions of signal, leader, linker, and carbohydrate-binding domain indicated low homology (73-74%). These variations in sequence homology are significant and could contribute to the structure and function of the enzyme.
Anamika Sharma,Vikrant Nain,Rameshwar Tiwari,Surender Singh,Anurup Adak,Pawan Kumar Singh Nain,Lata Nain 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.3
The present investigation was aimed towards pretreatment optimization of corncob to maximize cellulose and hemicellulose recovery, followed by substrate selection for holocellulase production using psychrotolerant Aspergillus niger SH3. Dilute alkali pretreatment (1.5% NaOH) resulted in higher recovery of cellulose (59.66%) and hemicellulose (28.34%) from corncob, while corn stover proved to be the best substrate for holocellulase production. Further, saccharification was optimized by Box-Behnken design to select the suitable conditions for maximum sugar release from pretreated corncob. The optimum conditions for maximum sugar release were 8% (w/v) substrate loading, 11 FPU/gds enzyme loading at temperature 38 oC and pH 3.0 which resulted in 114.5% higher sugar yield (912mg/gds of pretreated biomass) as compared with un-optimized conditions (425.35mg/gds). Theoretical yield of 48.8% ethanol was achieved through simultaneous saccharification and fermentation (SSF) using pretreated corncob. This study illustrates the potential of different corn residues as a promising substrate for bioethanol production.