Biodegradation Of Silk Fabrics And Their Structure And Properties

Food,clothing,housing,transport and other daily necessities were the basic human beings.Different clothe on the period reflected the period and territory feature and was important evidence to study the period developmental levels.The Silk Road was the bridge which connected the ancient economic and culture communication between China and foreign country.There were lots of ancient textiles on Silk Road and these invaluable ancient textiles were the most significant discovery of archaeology on Silk Road.The unearthed textiles were invaluable for studying old Chinese history,archaeology science and were an important part of relic on our country.But for the special structure of textiles,textiles were severely damages under long burial period and were fragile when were unearthed.Therefore,it is necessary to study the degradation mechanism of textiles in order to protect these invaluable ancient textiles.The structure and possible enzymatic reaction of silk fabrics under the influence of three different enzymes are studied herein.One kind of microbial enzyme(Protease XIV)secreted from Aspergillus oryzae,and two kinds of enzymes(?-chymotrypsin and trypsin)extracted from animal were used to age the modern silk textiles.We found that the microbial enzyme shown significantly activities on silk fabrics under our experimental conditions.Therefore,we use protease XIV to age silk fabrics on different days to study the aging mechanism of microbial enzymes.What's more,we analyze the influence of five different fungal species on contemporary silk fabrics.These fungi were isolated from historical silk textile,which were unearthed from Shisong Bomb,Ningbo city,Zhejiang province and not cleaned.Shi Song Tomb was excavated in 2011 and some precious silk fabrics of the Southern Song Dynasty(1127-1279 AD)were unearthed for the first time.The biodegradation properties of these individual species were investigated through observation of the chemical and morphological structure of the silk fabrics.And we found that the fungi which were belonging to Aspergillus were more active than other microorganism.Therefore,we used two selected microorganisms(Penicillium chrysogenum and Aspergillus oryzae)to age contemporary silk,and studied the microorganism degradation mechanism.The micro-morphology of aged samples presented a different degrading behavior of biological degradation compared with heating and lighting aging.The results suggested intermolecular hydrogen bonds within crystalline and random region were destroyed in silk fiber causing the abscission of superficial micro-layer of silk fiber.Meanwhile,the reducing contents of Tyr of all three enzymatic aged samples indicated that the amorphous region was partly degraded into small molecules.For the further degradation process,the crystal region was gradually degraded.When the amorphous region were degraded,the contents of free radicals were reduced due to the loose structure of amorphous region;while for the degrading of crystal region,the contents of free radicals were increased due to the compact structure of crystal region.The microbial enzymes shown significantly activities on silk fabrics under our experimental conditions,which indicate the microorganism may have great effects on the degradation of ancient silk fabrics under burial environment.Both fungi had harmful effects on the mechanical properties of silk fabrics.The results suggested that ancient silk fabrics should be cleaned thoroughly to avoiding the damaged of microorganism.And microorganism should be prevented from inappropriate storage condition in order to preserve the historical objects and artifacts.