Preparation Of High-value Lipids From Silk Reeling Wastes Via Bioconversion

China is the largest silk-producing country in the word, and silk reeling industries playa decisive role in the national economy. Silk reeling enterprises often distribute in silkproducin places, where prevalently exists the characteristics with small-scale production andscattered distributions, leading to a severe waste of resources that the reeling leftovers richin sericin, silkworm pupa proteins and chrysalis oils are treated as offcuts to be notadequately utilized. Based on this background, this thesis taking silk reeling wastes as rawmaterials managed to turn the wastes into treasures by successfully constructing the efficientbiorefinery systems to prepare the green energies like biodiesels, in which thebiotransformation from the reeling wastes to high-value oils had been achieved. Theconcrete results were as following:A simple, rapid and quantitative method for preparing fatty acid methyl esters (FAMEs)for assessing fatty acid content of silkworm pupae oils using chromatographic (GC) withtwo-step methylation and GC-mass spectrometry (GC-MS) had been developed. Silkwormpupa oil firstly was reacted with potassium hydroxide (10N) solution and methanol at55oCfor1.5h. After cooling to room temperature, it was inverted to continue methylating at55oCunder the same condition. FAMEs were extracted by n-hexane. Components were identifiedby GC-MS and contents were removed for GC-Flame Ionization Detector (GC-FID)analysis of gradient temperature program, which met successfully the demands of thequalitative and quantitative analysis of fatty acids in silkworm pupa oil.Taken an oleaginous yeast as the cultivation microorganism, the feasibility of thebiotransformation from silkworm reeling proteins to oils was explored. And put silk reelingwastes as the only nitrogen source, a new model to cultivate oleaginous microorganismswas established. The results showed when the value of protein in silk reeling wastewaterreached1.5g/L,3.59g/L of biomass and2.33g/L of oil production could be attained，andthat when the value of protein in silkworm chrysalis protein hydrolysate arrived at1.3g/L,4.36g/L of biomass and2.53g/L of oil production could be attained.In order to improve the bioavailability of oleaginous microorganisms, a newtechnology to treat defatted silkworm chrysalis under ultrasonic combing ionic liquid withenzyme was build. Effects of the pretreatment method of silkworm pupa protein oncultivation of oleaginous microorganisms and its synthetic grease were investigated. The results showed that when the material ratio of silkworm chrysalis protein and ionic liquid of1:10, ultrasonic treatment time of40min, tryptic concentration of3%, hydrolysistemperature of55°C and hydrolysis time of30min, the hydrolysis degree of silkwormchrysalis protein could come to32%. Using this protein hydrolyzate to cultivate yeast forproducing oil,14.33g/L of biomass was get. Compared with treatment by hot water,biomass was increased by2.39-fold.A novel two-step process with acid and base catalysts to prepare biodiesel fromhigh-value silkworm pupae oil was established. Choosing acid value of silkworm pupae oiland the yield of biodiesel as indicators, the conditions of pre-esterification andtransesterification process were optimized by one-factor experiment. More than95.17%yield of biodiesel was obtained, and the optimum results were as followed: with resin HD-8as an acid catalyst, mass ratio of methanol to oil of9:1, reaction temperature of70°C,catalyst content of3%, the acid value of silkworm pupae oil dropped to3.03mg KOH/gfrom6.06mg KOH/g; with KOH as base catalyst, reaction temperature of40°C, mass ratioof methanol to oil of5:1, catalyst content of2%, and reaction time of10min.Mulberry branch and other biological raw materials containing carbohydrates wereused to prepare solid-acid catalyst, and then used for the preparation of biodiesel. Thecatalytic properties and physical and chemical characterizations were investigated, so as toreplace commercial soild acid catalysts. The characterization results of scanning electronmicroscope (SEM), fourier transform infrared spectroscopy (FTIR), thermogravimetricanalysis (TGA) indicated that biological waste-based solid acid catalysts with sulfonatedgroups could be used in catalytic reaction. With mulberry branch solid acid as catalyst, massratio of methanol to oil of9:1, catalyst content of2%, reaction temperature of70°C andreaction time of15min, the acid value of silkworm pupae oil fell to1.63mg KOH/g from3.25mg KOH/g, and92.38%yield of biodiesel was acquired.In this thesis, silk reeling wastes were converted into high-value lipids with theprinciple of bioconversion firstly in domestic, and it provided a new method for dispose ofsilk reeling wastes properly and preparation of high-value lipids.