Carbon substrate-related

The unlimited growth-related type of poly(3HB) synthesis is most suited to one-stage continuous cultivation. This can be performed in a chemostat with carbon substrate limitation. The poly(3HB) content of the cells can be further... 

Several factors affect the overall economics of PHA production. These include PHA productivity, PHA content, yield of PHA on carbon source, carbon substrate cost, and recovery method employed. Figure 1 shows the production costs of P(3HB) by various P(3HB) contents and P(3HB) productivities [29]. The effect of P(3HB) productivity on the production cost is only related to the cost of the fermentation equipment [18]. However, the P(3HB) content has multiple effects on the volume of the fermentation equipment and the recovery process [17,18]. The increase of P(3HB) yield on carbon source and the use of less expensive carbon substrates reduce the cost of carbon substrate [17, 29]. Development of an efficient recovery method, which will be different for each bacterium employed, is also important to overall economics of PHA production. When the actual fermentation processes employing many different re-... 

Many Pseudomonas strains accumulate MCL-PHAs from alkane, alkene, al-kanoate, alkenoate, or alkanol [5,6,14,96]. The composition of the PHAs formed by the pseudomonads of the rRNA homology group I is directly related to the structure of the carbon substrate used [6]. These results suggested that MCL-PHAs are synthesized from the intermediates of the fatty acid oxidation pathway. In almost all pseudomonads belonging to the rRNA homology group I except Pseudomonas oleovorans, MCL-PHA can also be synthesized from acetyl-CoA through de novo fatty acid synthetic pathway [97]. The -oxidation pathway and de novo fatty acid synthetic pathway function independently in PHA biosynthesis. 

Comparable to the situation for the sialic acid and KDO lyases (vide supra), sets of stereochemically complementary pyruvate lyases are known, e,g. in Pseudomonas strains, which act on related 2-keto-3-deoxy-aldonic acids [112]. The enzymes cleaving six-carbon sugar acid phosphates—the KdgA and 2-keto-3-deoxy-6-phospho-D-galactonate (20) aldolases (KDPGal aldolase EC 4.1.2.21) [139] — are typified as class I enzymes, whereas those acting on non-phosphorylated five-carbon substrates — 2-keto-3-deoxy-L-arabonate (21) (KDAra aldolase EC 4.1.2,18) [140, 141] and 2-keto-3-deoxy-D-xylonate (22)... 

Analysis of the results obtained so far shows that substrate concentrations of 10,20, and 40 g/L were quite adequate to produce biosurfactant by B. subtilis ATCC 6633, although the maximum concentration of the product was observed for 10 g/L of commercial sugar. Therefore, it should be concluded that the carbon/nitrogen relation in the range of 6.4-25.6 g/g had no affect on the biosurfactant synthesis. 

Finally, although the All desaturase from cabbage looper is probably the most studied enzyme involved in these pathways, much more work should be done with it and related enzymes. For example, it only produces Z products and does not function efficiently with 14 carbon substrates, indicating a fundamental difference with the enzyme from redbanded leafroller moths, which desaturates 14-carbon acids to give a mixture of Z and E product (22). Projects such as this may well prove technically difficult, but will provide great insight into the enzymatic mechanisms. 

Selected waste related carbon substrate utilization by PNSB... 

Basically, the problem of instability of chain-like carbon is related to low stability of the free ensemble of the free linear-chain carbon clusters with sp -type a electron hybridization. The stability of linear-chain carbon can be improved if the chains grow on the surface of a substrate, as one end of the carbon chain becomes fixed on the substrate surface. The stability of chainlike carbon can also be enhanced as a result of the parallel growth of carbon chains in the perpendicular direction to the substrate surface [9]. 

Bis(phenylsulfonyl)methane has also been employed as an acidic carbon pronucleophile related to malonates and 1,3-diketones with success in the Michael reaction with ot,p-unsaturated aldehydes using 31c as catalyst (Scheme 3.6). The reaction showed a remarkable substrate scope when alkyl-substituted enals were employed but failed when cinnamaldehyde was tested as Michael acceptor. Alternatively, a more acidic cyclic gem-bissulfone has been used as Michael donor, keeping the high yields and enantioselectivities observed for the reaction and also allowing to expand the scope of the reaction to several aromatic enals.In all cases, the chemistry of the sulfonyl group was employed to generate a methyl group after metal-mediated desulfuration or, alternatively. 

PHA Structure Related to Microorganism Host and Carbon Substrate... 

Recent literature data on the molecular structure elucidation of biosurfactants have shown that, depending on different kinds of carbon substrates, it may be possible to obtain more structurally diverse versions of well-known products, e.g., variations of chain lengths of fatty adds. In the following, these related compounds have not been classified to the last-decade biosurfactants, which are substantially new-type products. 

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