Synthesis of Biopolymers

Abstract A number of polymers can be produced via fermentation, using special 

Biorelated Polymers Sustainable Polymer Science and Technology 

Edited by Chiellini et ah, Kluwer Academic/Plenum Publishers, 2001 127 

---

Oluwafemi, O. S and Adeyemi, O. O. (2010). One -pot room temperature synthesis of biopolymer -capped ZnSe nanoparticles. Journal of Materials Letters, 64, 2310-2313. 

Chemical activation is indeed the weak point of the prebiotic chemistry of polycondensation. In principle, this should be a prebiotic activation, namely a kind of spontaneous reaction under prebiotic conditions. Several more or less friendly activation methods have been used in the field, and most of them cannot, reasonably, be called prebiotic. On the other hand, the chemist must start working with some tool at hand. Let us now take a few examples from the literature on the prebiotic synthesis of biopolymers. 

The synthesis of biopolymers in vivo leads to macromolecules with a defined sequence of units. This effect is very important for living organisms and is different in comparison with random copolymerization in which sequences of units are distributed according to stochastic rules. On the other hand, the predicted sequence of units can be achieved by a set of successive reactions of respective monomer molecule addition. In template copolymerization, the interaction between comonomers and the template could pre-arrange monomer units defining sequence distribution in the macromolecular product. 

Only a few publications have appeared in the literature on template copolycondensation, in spite of the fact, that the process is very important to understand the mechanisms of processes similar to natural synthesis of biopolymers. General mechanism of this reaction can be considered in terms of the examples of template step homopolymerization. A few published systems will be described in the Chapter 5. 

For many years, most efforts directed towards the development of solid-phase preparations of alcohols had been limited to the synthesis of biopolymers, such as oligonucleotides and oligosaccharides. Interest in the preparation and chemical transformation of all types of alcohol on insoluble supports only began to grow rapidly in the early 1990s, when chemists realized the potential of parallel solid-phase synthesis for high-throughput compound production. 

In 1963 R. B. Merrifield published his seminal paper on the possibility of peptide synthesis on a solid, polymeric support [1], On the basis of this work, which helped its author to get the Nobel Prize in 1984, the field of chemical synthesis of biopolymers was developed and has been an area of great interest since then. It is therefore not surprising that the annual number of citations of this publication ( in Fig. 1, up to Autumn 1997 3511 in total ) increased rapidly between 1975 and 1990 and has now stayed at a very high level with only a slight tendency to fall. 

Polyketide synthases, fatty acid synthases, and non-ribosomal peptide synthetases are a structurally and mechanistically related class of enzymes that catalyze the synthesis of biopolymers in the absence of a nucleic acid or other template. These enzymes utilize the common mechanistic feature of activating monomers for condensation via covalently-bound thioesters of phosphopantetheine prosthetic groups. The information for the sequence and length of the resulting polymer appears to be encoded entirely within the responsible proteins. 

Several architectural paradigms are known for polyketide and fatty acid synthases. While the bacterial enzymes are composed of several monofunctional polypeptides which are used during each cycle of chain elongation, fatty acid and polyketide synthases in higher organisms are multifunctional proteins with an individual set of active sites dedicated to each cycle of condensation and ketoreduction. Peptide synthetases also exhibit a one-to-one correspondence between the enzyme sequence and the structure of the product. Together, these systems represent a unique mechanism for the synthesis of biopolymers in which the template and the catalyst are the same molecule. 

Biologic Background Technical Background Synthesis of Biopolymers Solid-Phase Synthesis of Small Molecules... 

The solid-phase synthesis of biopolymers via iterative coupling of monomeric building blocks has found widespread application. It can be adapted easily for the incorporation of non-natural building blocks or labeled monomers, which will be used as probe molecules in chemical biology. 

Synthesis on solid supports was first developed by Merrifield [1] for the assembly of peptides. It has expanded to include many different applications including oligonucleotide, carbohydrate, and small-molecule assembly (see Chapters 11 and 14). The repetitive cycle of steps involved in the solid-phase synthesis of biopolymers can be performed manually using simple laboratory equipment or fully automated with sophisticated instrumentation. This chapter examines typical solid-phase reaction kinetics to identify factors that can improve the efficiency of both manual and automated synthesis. The hardware and software features of automated solid-phase instruments are also discussed. The focus of this discussion is not on particular commercial model synthesizers but on the basic principles of instrument operation. These considerations can assist in the design, purchase, or use of automated equipment for solid-phase synthesis. Most contrasting features have advantages and disadvantages and the proper choice of instrumentation depends on the synthetic needs of the user. 

The cell as a biosynthesis machine can use cheap carbon sources (waste products) as precursor substrates to produce bacterial polymers. However, the in vitro synthesis of biopolymers requires costly purified key enzymes and precursor molecules such as ATP, coal, coal bolsters, and nucleotide sugars or sugar acids to synthesize polymers such as PHA, cellulose, alginate, and PGA. Consequently, these polymers have limited commercial applicability due to their very high production costs. It is estimated the production of PHB by in vitro synthesis would amount to a cost of around US 286,000 per gram of PHB whereas, bacterial production of PHB was estimated to cost about 0.0025 per gram of PHB, and this is still 5-10 times as expensive to produce as the respective petroleum-based polymers. 

An important feature of soluble polymer-bound libraries lies in the fact that biological screening can be performed in the standard format and that reactions can easily be monitored using H-NMR- and C-NMR spectroscopy. For the synthesis of biopolymers such as peptides CD spectroscopy was employed, e.g. for the synthesis of myoglobin 66-73. ... 

---