生物基材料

最近几年，由于可能的石油危机以及不断提高的环保要求，与国际上大多数国家一样，我国政府和各种投资机构加大了对环境友好材料的投入，特别是用可再生原料通过生物转化获得生物高分子材料或者单体，然后进一步开发各种应用产品。在聚羟基脂肪酸酯（PHA）、聚乳酸（PLA）、聚丁二酸丁二酯（PBS）、生物乙醇（PE）、生物尼龙（PTT）、生物导电材料和聚氨基酸等材料方面，我国取得了长足的进步，同时形成了一批企业。在特种高分子材料方面，我国高校和企业合作，利用微生物转化得到了以苯环为基本结构的单体，正在开发一系列含苯的高性能材料。可以认为，在生物材料制造领域，我国与世界先进水平的差距不大，在一些方面，我们甚至是领先的。但是，一些相关的基础研究必须大力开展，否则生物材料领域还是无法与传统的石油基材料竞争。本文讨论了生物材料领域相关基础研究问题、进展及发展趋势。

Biobased Materials

Bio-based plastics (Biomaterials) have been developed rapidly due to the raising petroleum prices and environmental concerns related to plastic pollution. Increasingly, reduction on CO_2 emission has become another reason for promoting bio-based plastics (materials) amid the worldwide financial tsunami. Generally speaking, bio-based plastics include starch based plastics, protein (soybean protein) based plastics, cellulose blended plastics. They can also be blended with conventional plastics like polyethylene (PE), polypropylene (PP) or polyvinyl alcohol (PVA). However, such bio-based plastics are only partially biodegradable. The residual petroleum based plastics remain as broken pieces, creating additional pollution. In addition, these plastics have intrinsic thermo- and mechanical weaknesses, they are now discouraged for applications. To produce bio-based plastics completely resembling conventional plastics, bacteria are employed to make building blocks for plastic polymers from renewable sources including starch, cellulose, fatty acids and whatever bacteria can consume for growth. So far, following building blocks can be microbially produced for polymerization purposes: Hydroxyalkanoic acids with many structural variations, lactic acid, succinic acid, 3-hydroxypropionic acid, bio-ethylene produced from dehydration of bio-ethanol, 1,3-propanediol and cis-3,5-cyclohexadien-1,2-diols (abbreviated as DHCD) from microbial transformation of benzene et al, are common monomers produced by microbial transformation. They have been successfully used for making various bacterial plastics (biomaterials). In biobased materials R&D, China has paid close attentions to them and has developed some advanced technologies for their production and applications. This chapter will deal with some basic scientific and engineering issues that limit the development of these novel biomaterials.