3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

There is huge variability among yeasts with regard to their efficiency in utilizing glycerol as the sole source of carbon and energy. Certain species show growth rates with glycerol comparable to those reached with glucose as carbon source; others are virtually unable to utilize glycerol, especially in synthetic medium. Most of our current knowledge regarding glycerol uptake and its catabolic pathways has been gained from studying laboratory strains of the model yeast Saccharomyces cerevisiae. The growth of these strains on glycerol is dependent on the presence of medium supplements such as amino acids and nucleobases. In contrast, there is only fragmentary knowledge about S. cerevisiae isolates able to grow in synthetic glycerol medium without such supplements as well as about growth of non-Saccharomyces yeast species on glycerol. Thus, more research is required to understand why certain strains and species show superior growth performance on glycerol compared to common S. cerevisiae laboratory strains. This minireview summarizes what is known so far about the gene products and pathways involved in glycerol metabolism and transport in yeast and fungi as well as the regulation of these processes. This article is protected by copyright. All rights reserved.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1462-2920.13617

Glycerol metabolism and transport in yeast and fungi: established knowledge and ambiguities.

The functional reconstruction of acetoin and meso-2,3-butanediol (meso-2,3-BD) biosynthetic pathways in Escherichia coli have been explored systematically. Pathway construction involved the in vsivo screening of prospective pathway isozymes of yeast and bacterial origin. After substantial engineering of the host background to increase pyruvate availability, E. coli YYC202(DE3) ldhA(ilvC( expressing ilvBN from E. coli and aldB from L. lactis (encoding acetolactate synthase and acetolactate decarboxylase activities, respectively) was able to produce up to 870 mg/L acetoin, with no coproduction of diacetyl observed. These strains were also found to produce small quantities of meso-2,3-BD, suggesting the existence of endogenous 2,3-BD dehydrogenase activity. Finally, the coexpression of bdh1 from S. cerevisiae, encoding 2,3-BD dehydrogenase, in this strain resulted in the production of up to 1120 mg/L meso-2,3-BD, with glucose a yield of 0.29 g/g. While disruption of the native lactate biosynthesis pathway increased pyruvate precursor availability to this strain, increased availability of NADH for acetoin reduction to meso-2,3-BD was found to be the most important consequence of ldhA deletion.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/biot.200900279

Metabolic engineering of acetoin and meso-2, 3-butanediol biosynthesis in E. coli.

Background
2,3-Butanediol (2,3-BD), a platform and fuel bio-chemical, can be efficiently produced by Klebsiella pneumonia, K. oxytoca, and Serratia marcescens. However, these strains are opportunistic pathogens and not favorable for industrial application. Although some generally regarded as safe (GRAS) microorganisms have been isolated in recent years, there is still a demand for safe 2,3-BD producing strains with high productivity and yield under thermophilic fermentation.

/pdf/a-newly-isolated-bacillus-licheniformis-strain-1r2hoqhrom.pdf

A newly isolated Bacillus licheniformis strain thermophilically produces 2,3-butanediol, a platform and fuel bio-chemical

A novel approach appropriate for rapid separation and immobilization of a single cell by concomitantly utilizing laser manipulation and locally thermosensitive hydrogelation is proposed in this paper. We employed a single laser beam as optical tweezers for separating a target cell and locating it adjacent to a fabricated, transparent micro heater. Simultaneously, the target cell is immobilized or partially entrapped by heating the thermosensitive hydrogel with the micro heater. The state of the thermosensitive hydrogel can be switched from sol to gel and gel to sol by controlling the temperature through heating and cooling by the micro heater. After other unwanted cells are removed by the high-speed cleaning flow in the microchannel, the entrapped cell is successfully isolated. It is possible to collect the immobilized target cell for analysis or culture by switching off the micro heater and releasing the cell from the entrapment. We demonstrated that the proposed approach is feasible for rapid manipulation, immobilization, cleaning, isolation and extraction of a single cell. The experimental results are shown here.

On chip single-cell separation and immobilization using optical tweezers and thermosensitive hydrogel

In applied microbiology, strain improvement of microorganisms by conventional selection culture is not always successful, so single-cell selection of viable cells with the desired characteristics from a large heterogeneous population may be used instead. Single-cell selection with use of a micromanipulator is possible, but laborious. For many applications, the process has been automated. In this review, an automated method, laser scanning cytometry (LSC), is outlined together with flow cytometry (FCM). FCM is familiar to many microbiologists, but LSC is a microscopic-slide-based method that is less well known. One of its advantages is its possible use in the examination of small cell populations. In addition, individual cells can be examined repeatedly, measured automatically and later observed microscopically by the operator, and finally stored (if desired) on the microscopic slide on which they are placed. Fluorescent and other probes are available in abundance for FCM, and almost all might be used in LSC. A number of applications of these methods are cited from the extensive literature (mostly about FCM), but the list of possible applications in this review is far from being exhaustive. This review is intended as an introduction for the applied microbiologist to the manifold uses of LSC.

Single‐Cell Sorting of Microorganisms by Flow or Slide‐Based (Including Laser Scanning) Cytometry

For the production of chiral compounds, an Escherichia coli HB 101 strain was transformed. A chiral column that could resolve the three 2,3-butanediol isomers and the two acetoin isomers was used to demonstrate the stereospecificity of the enzyme. The H.polymorpha DL-1 gene product, glycerol dehydrogenase, catalyses the NAD + -dependent oxidation of 2,3-butanediol to acetoin as well as the corresponding reverse reactions. The recombinant E. coli HB101 strain harbouring the expression plasmid produced (3R)-acetoin [99% yield, >99.9% enantiomeric excess (e.e.)] from 110 mM (2R, 3R)-2,3-butanediol and (3S)-acetoin (99% yield, >99.9% e.e.) from 110 mM meso-2,3-butanediol after 24 h of incubation, showing specificity towards the secondary alcohol in R-configuration. From a racemate of 110 mM 2,3-butanediol (the molar ratio of 17 (2R, 3R): 15 (2S, 3S): 78 (meso)), (2S,3S)-2,3-butanediol (15 mM, 92% e.e.) was obtained in the resting-cell reaction without any additive to regenerate NAD + from NADH.

Expression of the gene of glycerol dehydrogenase from Hansenula polymorpha Dl-1 in Escherichia coli for the production of chiral compounds

Glycerol dehydrogenase (EC 1.1.1.6) was purified from a methylotrophic yeast, Hansenula polymorpha DL-1, for the characterisation and identification of its function. The yeast was grown in a glycerol medium. SDS-PAGE and gel permeation chromatography showed the enzyme to be composed of two subunits, each with a molecular mass of 36,000. The optimum pH for glycerol oxidation was 10. The optimum temperature for enzyme activity was 30 °C. CuCl 2 , HgCl 2 , and FeCl 3 were severely inhibitory. The activity decreased to 0% by 1 mM 2, 2'-dipyridyl and o-phenanthroline, which are inhibitors for the Fe 2+ -enzyme. An SH reagent, p-chloromercuribenzoate, was strongly inhibitory at 0.1 mM. The enzyme showed greater activity towards (R)-1,2-propanediol and (2R,3R)-2,3-butanediol than towards glycerol. No activity was detected towards 1.3-propanediol, ethanol, 1-propanol, 2-propanol, propionic acid, 1,4-butanediol, 1,2,3,4-butanetetraol, sorbitol, and L-iditol. The ratios of the activity for the R-form to that of the S-form were 5.0(R): 1(S) and 38 (R): 1(S) for 1,2-propanediol and 2,3-butanediol, respectively. The K m values for glycerol and dihydroxyacetone were 118 mM and 4.87 μM, respectively. The gene encoding the enzyme was cloned from an H. polymorpha DL-1 genomic library. Reverse transcription PCR showed that the mRNA of the enzyme was synthesised in cells grown on methanol as well as on glycerol. In the deduced amino acid sequence of 380 residues of the glycerol dehydrogenase of H. polymorpha DL-1, the NAD(H) binding pattern and the cysteine residues that correspond to the cysteine ligands at the zinc atom were conserved, as they are in sorbitol dehydrogenase, L-iditol 2-dehydrogenase, and 2,3-butanediol dehydrogenase from other origins.

Characterisation of Glycerol Dehydrogenase from a Methylotrophic Yeast, Hansenula polymorpha Dl‐1, and its Gene Cloning

Chiral alcohols are useful as intermediates for the synthesis of drugs. In the production of chiral alcohols, microbial enzymes are promising since high optical purity is required. Under these conditions, the reaction by resting cells is more convenient and inexpensive than by an enzyme reaction. Chiral 1,2-propanediol and 2,3-butanediol were obtained using cells expressing the enzyme which demonstrated high stereospecificity. By means of recombinant cells expressing the glycerol dehydrogenase of Hansenula polymorpha DL-1, the medium was enriched with (S)-1,2-propanediol (98 % enantiometric excess, e.e.) during a 24-h incubation, whereas the (R)-form was removed from 100 mM of the racemate (R:S = 1:1). For an asymmetric reduction, a recombinant was constructed which also expressed the glucose dehydrogenase gene of Bacillus subtilis origin as an NADH reproducer. In the resting cell reaction, the pH control at 7.5 promoted the conversion from ketone to alcohol. (2R,3R)-2,3-butanediol (e.e. > 99.9 %; 308 mM) was produced from 800 mM acetoin (R:S = 3:4); (R)-1,2-propanediol (e.e. > 99.9 %; 550 mM) from 800 mM acetol in a 33-h incubation by the addition of glucose and ketone with pH control. In this reaction, (S)-forms of both 2,3-butanediol and 1,2-propanediol were not produced. The pH control and feeding of the substrates were uncomplicated. The production process of the chiral alcohol by the recombinants which expresses glycerol dehydrogenase proved convenient.

Synthesis of Optically Active Diols by Escherichia coli Transformant Cells that Express the Glycerol Dehydrogenase Gene of Hansenula polymorphaDL‐1

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Single‐Cell Sorting of Microorganisms by Flow or Slide‐Based (Including Laser Scanning) Cytometry

Expression of the gene of glycerol dehydrogenase from Hansenula polymorpha Dl-1 in Escherichia coli for the production of chiral compounds

Characterisation of Glycerol Dehydrogenase from a Methylotrophic Yeast, Hansenula polymorpha Dl‐1, and its Gene Cloning

Synthesis of Optically Active Diols by Escherichia coli Transformant Cells that Express the Glycerol Dehydrogenase Gene of Hansenula polymorphaDL‐1