Engineering an artificial pathway for Cis-Α-irone biosynthesis

Please click Additional Files below to see the full abstrac

Engineering an artificial pathway for Cis-alpha-irone biosynthesis

Please click Additional Files below to see the full abstrac

Real-time monitoring for brain tissue deformation during surgery

As conventional open surgical techniques are fast being replaced with recent advanced techniques that are either minimally invasive or completely non-invasive, the development in Image-Guided NeuroSurgery (IGNS) has played a pivotal function in minimizing invasive neurosurgery. However, inIGNS a major source of concern is error due to brain tissue dislocation and deformation during neurosurgical standard operating procedures (SOP).Master of Science (Biomedical Engineering

Classification of medical images for disease diagnosis

This report analyses how a mathematical model of the form, y=M*exp (-t/a)*(1-exp (-t/b)) +N*exp (t*c), emulating the function of the kidneys was formulated and developed using the MATLAB environment. The kidneys perform the essential function of removing waste products from the blood and regulating the water fluid levels. For the classification of the medical images, a Statistical Pattern Recognition approach, Linear Discriminant Analysis (LDA) was employed. A database comprising of over 40 renograms, taken from more than 20 renal patients was used for this project. The algorithm was first trained using the renograms, called the training set and then further developed using the test sets. The results obtained verified that the algorithms have been successfully implemented in the program written by the author.Bachelor of Engineerin

Involvement in Denitrification is Beneficial to the Biofilm Lifestyle of Comamonas testosteroni: A Mechanistic Study and Its Environmental Implications

Comamonas is one of the most abundant microorganisms in biofilm communities driving wastewater treatment. Little has been known about the role of this group of organisms and their biofilm mode of life. In this study, using Comamonas testosteroni as a model organism, we demonstrated the involvement of Comamonas biofilms in denitrification under bulk aerobic conditions and elucidated the influence of nitrate respiration on its biofilm lifestyle. Our results showed that C. testosteroni could use nitrate as the sole electron acceptor for anaerobic growth. Under bulk aerobic condition, biofilms of C. testosteroni were capable of reducing nitrate, and intriguingly, nitrate reduction significantly enhanced viability of the biofilm-cells and reduced cell detachment from the biofilms. Nitrate respiration was further shown to play an essential role in maintaining high cell viability in the biofilms. RNA-seq analysis, quantitative polymerase chain reaction, and liquid chromatography-mass spectrometry revealed a higher level of bis(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) in cells respiring on nitrate than those grown aerobically (1.3 × 10-4 fmol/cell vs 7.9 × 10-6 fmol/cell; P < 0.01). C-di-GMP is one universal signaling molecule that regulates the biofilm mode of life, and a higher c-di-GMP concentration reduces cell detachment from biofilms. Taking these factors together, this study reveals that nitrate reduction occurs in mature biofilms of C. testosteroni under bulk aerobic conditions, and the respiratory reduction of nitrate is beneficial to the biofilm lifestyle by providing more metabolic energy to maintain high viability and a higher level of c-di-GMP to reduce cell detachment.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Accepted versio

Engineering an artificial pathway for cis-alpha-irone biosynthesis

International audienc

Involvement in Denitrification is Beneficial to the Biofilm Lifestyle of <i>Comamonas testosteroni</i>: A Mechanistic Study and Its Environmental Implications

Comamonas is one of the most abundant microorganisms in biofilm communities driving wastewater treatment. Little has been known about the role of this group of organisms and their biofilm mode of life. In this study, using Comamonas testosteroni as a model organism, we demonstrated the involvement of Comamonas biofilms in denitrification under bulk aerobic conditions and elucidated the influence of nitrate respiration on its biofilm lifestyle. Our results showed that C. testosteroni could use nitrate as the sole electron acceptor for anaerobic growth. Under bulk aerobic condition, biofilms of C. testosteroni were capable of reducing nitrate, and intriguingly, nitrate reduction significantly enhanced viability of the biofilm-cells and reduced cell detachment from the biofilms. Nitrate respiration was further shown to play an essential role in maintaining high cell viability in the biofilms. RNA-seq analysis, quantitative polymerase chain reaction, and liquid chromatography–mass spectrometry revealed a higher level of bis­(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) in cells respiring on nitrate than those grown aerobically (1.3 × 10^–4 fmol/cell vs 7.9 × 10^–6 fmol/cell; <i>P</i> < 0.01). C-di-GMP is one universal signaling molecule that regulates the biofilm mode of life, and a higher c-di-GMP concentration reduces cell detachment from biofilms. Taking these factors together, this study reveals that nitrate reduction occurs in mature biofilms of C. testosteroni under bulk aerobic conditions, and the respiratory reduction of nitrate is beneficial to the biofilm lifestyle by providing more metabolic energy to maintain high viability and a higher level of c-di-GMP to reduce cell detachment

Microaerobic Fermentation Enables High-Titer Biosynthesis of the Rose Monoterpenes Geraniol and Geranyl Acetate in Escherichia coli

Monoterpenes are commercially important flavors and fragrances with high demand. Microbial production of monoterpenes is more sustainable than plant extraction, however, it is restricted by high product toxicity/volatility and inefficient monoterpene synthases. Hence, most reported monoterpene titers are still low for commercialization. To overcome these challenges, we utilized the rose NUDIX hydrolase instead of geraniol synthase to produce geraniol in E. coli. The supply of the monoterpene precursor, geraniol pyrophosphate (GPP), was enhanced by the mevalonate pathway optimization and screening/engineering of various GPP synthases from plants, yeasts, and bacteria. Furthermore, geraniol production was improved by deleting the competing pathway genes (tnaA, yjgB, and ackA-pta) and optimizing the bioprocess. The final strain produced 1.05 g/L monoterpenes in total including 0.91 g/L geraniol in flasks. Moreover, the geraniol strain was reprogrammed to produce geranyl acetate, reaching ∼4.1 g/L in flasks from 20 g/L glycerol (∼66% of theoretic yield). We observed that microaerobic fermentation is critical to achieve high-yield production of geraniol and geranyl acetate. By controlling the redox potential at −190 mV in 5 L bioreactors, our strain produced ∼19 g/L geranyl acetate in 100 h, with a yield of 0.12 g/g-glycerol

Total enzymatic synthesis of cis-α-irone from a simple carbon source

International audienceAbstract Metabolic engineering has become an attractive method for the efficient production of natural products. However, one important pre-requisite is to establish the biosynthetic pathways. Many commercially interesting molecules cannot be biosynthesized as their native biochemical pathways are not fully elucidated. Cis-α-irone, a top-end perfumery molecule, is an example. Retrobiosynthetic pathway design by employing promiscuous enzymes provides an alternative solution to this challenge. In this work, we design a synthetic pathway to produce cis-α-irone with a promiscuous methyltransferase (pMT). Using structure-guided enzyme engineering strategies, we improve pMT activity and specificity towards cis-α-irone by >10,000-fold and >1000-fold, respectively. By incorporating the optimized methyltransferase into our engineered microbial cells, ~86 mg l −1 cis-α-irone is produced from glucose in a 5 l bioreactor. Our work illustrates that integrated retrobiosynthetic pathway design and enzyme engineering can offer opportunities to expand the scope of natural molecules that can be biosynthesized