ASSESSMENT OF POLYHYDROXYALKANOATE SYNTHESIS IN SUBMERGED CULTIVATION OF Cupriavidus necator AND Burkholderia cepacia STRAINS USING SOYBEAN AS SUBSTRATE

ABSTRACT Polyhydroxyalkanoates (PHA) are biocompatible and biodegradable polyesters produced by prokaryotic microbes for energy storage and carbon reserve. These polymers are an option to diminish the massive impact caused by inadequate disposal of synthetic plastics. In this study, evaluation and characterization of PHA produced by Cupriavidus necator (IPT 026 and IPT 027) and Burkholderia cepacia (IPT 119 and IPT 400), using soybean as substrate, were carried out (soybean 15 g L-1, pH 7.0, 150 rpm, 72 hours). The highest polymer production was achieved using IPT 027 (0.84 ± 0.07 g L-1). All PHA produced showed the characteristic bands of polyester functional groups in the FTIR spectra. Polymers synthesized by Cupriavidus necator exhibited initial temperatures of degradation superior to 300oC and higher molecular weights than the ones produced by Burkholderia cepacia, which in turn, exhibited lower crystallinity (inferior to 30%), revealing high influence of the microorganism strain on PHA properties and production.摘要 聚羟基脂肪酸酯（Polyhydroxyalkanoates，PHA）是一类由原核微生物合成的兼具生物相容性与生物可降解性的聚酯，可用于能量储存与碳储备。此类聚合物可有效缓解合成塑料不当处置所引发的严重环境危害。本研究以大豆为底物，对坏死贪铜菌（Cupriavidus necator，IPT 026与IPT 027）及洋葱伯克霍尔德菌（Burkholderia cepacia，IPT 119与IPT 400）合成的PHA进行了产量评价与理化表征，实验参数设置为：大豆底物浓度15 g·L⁻¹、初始pH 7.0、摇床转速150 rpm、培养时长72小时。实验结果显示，IPT 027菌株的聚合物产量最高，可达(0.84±0.07) g·L⁻¹。所有制备得到的PHA样品在傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy，FTIR）中均呈现出聚酯官能团的特征吸收峰。由坏死贪铜菌合成的聚合物初始降解温度高于300℃，且分子量高于洋葱伯克霍尔德菌所制备的聚合物；后者的结晶度更低（不足30%）。上述结果表明，微生物菌株对PHA的性能与合成产量具有显著影响。