Suzuki Natsuhei, Suda Daito, Ngan Nguyen Thi Thuy, Gibu Namiko, Huong Nguyen Lan, Anh To Kim, Kasai Daisuke
Department of Materials Science and Bioengineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan.
School of Biotechnology and Food Technology, Hanoi University of Science and Technology, Hanoi 10000, Vietnam.
Microorganisms. 2022 Nov 24;10(12):2324. doi: 10.3390/microorganisms10122324.
Microbial degradation of natural rubber and synthetic poly(-1,4-isoprene) is expected to become an alternative treatment system for waste from poly(-1,4-isoprene) products including scrap tires. NBRC 15,532, a gram-positive rubber-degrading bacterium, can utilize poly(-1,4-isoprene) as the sole source of carbon and energy to produce oligo-isoprene metabolites containing aldehyde and keto end groups. A homology-based search of the genome revealed a gene encoding a latex-clearing protein (Lcp). Gene disruption analysis indicated that this gene is essential for the utilization of poly(-1,4-isoprene) in this strain. Further analysis of the genome sequence identified aldehyde dehydrogenase (ALDH) genes as potential candidates for oxidative degradation of oligo-isoprene aldehydes. Based on the enzymatic activity of the ALDH candidates, NF2_RS14000 and NF2_RS14385 may be involved in the degradation of oligo-isoprene aldehydes. Analysis of the reaction products revealed that these ALDHs oxidized tri- to penta-isoprene aldehydes, which were generated by the reaction of Lcp. Based on the inability of ALDH gene deletion mutants, we concluded that NF2_RS14000 is mainly involved in the utilization of poly(-1,4-isoprene) and the oxidative degradation of oligo-isoprene aldehydes in NBRC 15,532.
天然橡胶和合成聚（-1,4-异戊二烯）的微生物降解有望成为一种处理包括废旧轮胎在内的聚（-1,4-异戊二烯）产品废弃物的替代处理系统。革兰氏阳性橡胶降解菌NBRC 15532能够利用聚（-1,4-异戊二烯）作为唯一的碳源和能源，以产生含有醛基和酮基端基的低聚异戊二烯代谢产物。基于同源性的基因组搜索揭示了一个编码乳胶清除蛋白（Lcp）的基因。基因破坏分析表明，该基因对于该菌株利用聚（-1,4-异戊二烯）至关重要。对基因组序列的进一步分析确定醛脱氢酶（ALDH）基因是低聚异戊二烯醛氧化降解的潜在候选基因。基于ALDH候选基因的酶活性，NF2_RS14000和NF2_RS14385可能参与低聚异戊二烯醛的降解。对反应产物的分析表明，这些ALDH氧化了由Lcp反应产生的三至五聚异戊二烯醛。基于ALDH基因缺失突变体的无能，我们得出结论，NF2_RS14000主要参与NBRC 15532中聚（-1,4-异戊二烯）的利用和低聚异戊二烯醛的氧化降解。
