Crawford D L, Pometto A L, Crawford R L
Department of Bacteriology and Biochemistry, University of Idaho, Moscow 83843, USA.
Biotechnol Adv. 1984;2(2):217-32. doi: 10.1016/0734-9750(84)90006-5.
Lignin degrading strains of Streptomyces were grown on lignocelluloses from a variety of plant sources. These actinomycetes readily degraded the lignin present in the residues and released a major portion of the lignin into the growth medium as a water soluble, modified polymer. The polymer, an acid precipitable polyphenolic lignin (APPL), was recovered from spent culture media by acid precipitation or dialysis/lyophilization. APPL's were shown to be mostly free of nonlignin components. As compared to native lignin they were more oxidized, were especially enriched in phenolic hydroxyl groups, and were significantly reduced in methoxyl groups. The yield of APPL from different lignocelluloses correlated with their biodegradability. Grasses such as corn stover were the optimal lignocellulose type for APPL production by Streptomyces. In contrast white-rot fungi produced only small amounts of APPL as they decomposed lignin. A solid state bioconversion process was developed using Streptomyces viridosporus T7A to produce APPL from corn stover lignocellulose in yields >or= 30% of the initial lignin present in the substrate. APPL produced by S. viridosporus was examined for its properties and possible use as an antioxidant. The APPL was shown to have good antioxidant properties after mild chemical treatment to reduce the alpha-carbonyl groups present in the APPL. Oxidation of the APPL with hydroxyl radical (OH(*)) further improved its antioxidant properties probably as the result of aromatic ring hydroxylation reactions. As compared with currently used commercial antioxidants, the modified APPL was thought to be competitive when economics of production was considered. Native lignin on the other hand was shown to exhibit no antioxidant properties, even after reduction and/or oxidation.
链霉菌木质素降解菌株在来自多种植物来源的木质纤维素上生长。这些放线菌很容易降解残留物中存在的木质素，并将大部分木质素作为水溶性改性聚合物释放到生长培养基中。该聚合物是一种酸沉淀多酚木质素（APPL），通过酸沉淀或透析/冻干从用过的培养基中回收。结果表明，APPL基本不含非木质素成分。与天然木质素相比，它们的氧化程度更高，尤其富含酚羟基，甲氧基含量显著降低。不同木质纤维素产生APPL的产量与其生物降解性相关。玉米秸秆等草类是链霉菌生产APPL的最佳木质纤维素类型。相比之下，白腐真菌在分解木质素时只产生少量的APPL。开发了一种固态生物转化工艺，使用绿孢链霉菌T7A从玉米秸秆木质纤维素中生产APPL，产量≥底物中初始木质素的30%。对绿孢链霉菌产生的APPL的性质及其作为抗氧化剂的潜在用途进行了研究。经温和化学处理以减少APPL中存在的α-羰基后，APPL显示出良好的抗氧化性能。用羟基自由基（OH(*)）氧化APPL可能由于芳环羟基化反应进一步改善了其抗氧化性能。与目前使用的商业抗氧化剂相比，考虑到生产成本时，改性APPL被认为具有竞争力。另一方面，即使经过还原和/或氧化，天然木质素也没有抗氧化性能。
