Preparation of Citrus Peel and Pomace Bacterial Cellulose and Fabrication and Filtration of Air Filters

Author:Fan Zuo

Supervisor:pan si zuo

Database:Doctor

Degree Year:2019

Download:48

Pages:137

Size:7674K

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Bacterial cellulose(BC),which is named as nata in food industrial,is a nano scale cellulose from bacteria.BC is applied in various fields owing to its unique performances.However,high production costs restrict applications of BC.Citrus is the third largest international trade agricultural product in the world,and citrus peel and pomace accounts for 40 wt%-60 wt%of the total weight.At present,the recycling of citrus pomace consumes a lot of energy and the output value is low.To my knowledge,there have been no other studies utilising the citrus peel and pomace enzymolysis as a medium for producting BC.Air pollution has been a serious health hazard because of excessive human activities.A high-performance air filter can be used to resolve this problem.The nanofabrics from electrospinning have a high removal efficiency,but it has been challenging to control the porous structures to reduce the normalized pressure drop,in particular for thick fabrics.The general ideas are as follow:1)the present study aimed to investigate the suitability of citrus peel and pomace enzymolysis(CPPE)for the production of BC and to study the structural properties of BC films.After hydrolysis,the BC particles(BCPs)were obtained.2)BC and BCPs assembled with whey protein concentrate and zein to fabricate functional particles,respectively.The air filters are made of the particles and microcellulose fibers from wood pulp.3)we report a study on the development of a new strategy for the fabrication of multi-functional protein fabrics with novel ribbon morphology and cotton-candy-like structures.This study presents guidelines for the design of advanced fabrics for various filtration applications.We report protein/cellulose based air filters to address the issues of BC production cost,citrus peel and pomance reuse and air pollution.The main results are as follows:1.The strains are isolated from persimmon vinegar.Thecolonial morphology,physiological and biochemical characteristics,the G+C mol%content of the isolated strain are identified according to the"Common Bacterial Identification Manual"and"Berger’s Bacterial Identification Manual".The isolated stratin is belong to the Komagataeibacter,and the CPPE is used as a medium to produce BC.According to the results of single factor and orthogonal experiments,the optimum conditions for producing BC are as follows:enzyme content 0.3 wt%,enzymatic hydrolysis temperature 50°C,enzymatic hydrolysis time 6 h,material-water ratio7:3,inoculum amount 8%(v/v),yeast extract 0.4 g/100 mL,peptone 0.4 g/100 mL,ethanol 0.8mL/100 mL,incubation temperature 30°C and incubation time 8 d.The yield of BC from CPPE medium is 5.7±0.7 g/L,which is higher than the BC(3.9±0.6 g/L)from Hestrin-Schramm(HS)medium.To evaluate the structure of BC,FT-IR,XRD,chroma meter,SEM,DSC are utilised.BC is hydrolyzed by six different concentrations of sulfuric acid(SA)to obtain BCPs.BCPs/30wt%SA is selected for the following experiment in line with the single factor analysis.2.The interaction between BC and whey protein concentrate(WPC)is studied.The D-WPC is aborbed on the surface of BCPs by elecstrostatic interaction.After mixed with WP,the hierarchical D-WPC@BC/WP composite is obtained.The protein-functionalized nanocellulose can not only help expose the functional groups of protein for trapping pollutants but also act as a binder to reinforce the composite fabrics.At the same time,the long microcellulose fibers form large pores,reducing normalized pressure drop and improving mechanical properties.The structure and properties of D-WPC@BC/WP are studied by CD,SEM,a dynamic laser light scattering and a universal testing machine.Filtration performance experiments show that D-WPC@BC/WP composite with high filtration efficiency of above 85%for PM0.3 but extremely low normalized pressure drop of 0.194 kPa/g,which is only about 1%of that for protein nanofabrics constructed by electrospinning.In addition,D-WPC@BC/WP composite has a good mechanical property.3.In order to further improve the filtration performance of air filters,it is necessary to increase the quantity of protein nanoparticles.Here,we report an air filter with high filtration efficiency and low air pressure drop based on applying zein solution to generate protein-functionalized nanostructures.In specific,the air filter consists of BCPs/zein nanoparticles as active fillers prepared and porous structures of microfibers as the frame from wood pulp.The zein-protein coated nanoparticles,BCPs/zein nanoparticles,have multiple ways of contributions to improving removal efficiency for the filters.Firstly,the exposed functional groups of zein-protein help to trap air pollutants including toxic gasseous molecules via interaction mechanisms.Secondly,the nanoparticles with the high surface area promote the capture capability for small particulate pollutants.Meanwhile,the long-micron wood pulp fibers forming a frame with large pores significantly reduce the pressure drop.The air filter(F-Z15)with the high efficiency of above 93.71±1.31%for PM0.3,88.30±5.68%for HCHO and 60.71±4.23%for CO,but extremely low normalized pressure drop of 0.108 kPa/g was abtained.4.Based on the above research,it has been very challenging to simultaneously realize the high removal efficiency,low flow resistance,high filtration capacity of pollutants and the capability of removing different types of pollutants.Herein,we report a study on the development of a new strategy for the fabrication of multi-functional protein fabrics with novel ribbon morphology and cotton-candy-like structures to address the above challenges.In particular,a metastable solution of zein protein in a solvent mixture(acetone-butanol-DI water-2:1:1)to fabricate the ribbon-like fibres with self-curving behaviour.This self-curved zein fabric has multiple significant contributions to filtration.Firstly,the ribbon morphology notably enhances the trapping capability for sub-micron particulate pollutants in particular.Secondly,the self-curving feature of the fibres generates cotton-candy-like loose structures and elastic properties for the fabric,which significantly reduces the flow resistance.The unique structure and morphology of the ribbon fibers are confirmed and studied by SEM,TEM,rheometer and so on.As a result,the filtration performances have been simultaneously improved,including enhanced capture efficiency(99.9%for PM0.3),filtration capacity and stability of air pressure drop,as well as the reduced airflow resistance,as compared with traditional fabrics with rod fibres and the commercial air filter.