Добірка наукової літератури з теми "Ribbon retting"

Jute retting has become a major obstacle for cultivation of jute due to water scarcity. Not only that, the water retting generates waste water and causes environmental pollution. This experiment was conducted to extract fibre through a mechanical process instead of extracting traditional water retting to overcome the problem. Machine extraction and water retting methods were applied to non-retted ribbons. Physico- chemical properties were then determined of the extracted fibre samples. The promising result obtained that the fibre extraction from ribbon is possible by the developed fibre extractor machine. Machine extracted fibre of the bottom portion shows similar strength and luster property like water retted fibre of the bottom. Middle portion of the machine extracted fibre showed a significantly higher luster property compared to water retted middle portion. Machine extracted fibres were coarse compared to water retted fibre. Water retting process produced finer quality fibre. Machine extracted fibres contain lower cellulose, higher hemicellulose and higher lignin compared to water retted fibre. These results show the possibility of developing alternative bast fibre extraction processes employing machine not undergoing water retting method.

Jute is the golden fiber of Bangladesh, but its production is declining due to the involvement of higher production and processing costs, where a major portion of the cost is needed for fiber extraction. Labor unavailability and increasing labor cost have led to higher jute fiber production cost. To address these issues, this study looks at the development of a power-operated and cost-effective fiber extraction machine aiming at reducing the production cost. The study was conducted at the Rangpur regional office premises of Practical Action in Bangladesh, and the developed machine was branded as “Aashkol”, which had the following major parts: a feeding tray, a primary extraction roller, a secondary extraction roller, grabbing rollers, fiber collection stand, base frame, protection cover, and a spring-loaded tray under the primary extraction roller. The Aashkol can extract green ribbon from the jute stem, but jute sticks were broken down into smaller pieces (3–6 cm). The performance evaluation of the machine was conducted using different types of jute (Deshi, Kenaf, and Tossa) and compared with another jute extraction machine (KP model, introduced by Karupannya Rangpur Ltd.). The Aashkol-based extraction and improved retting systems were also evaluated and compared with traditional jute extraction systems. The jute stem input capacity (4.99 t h−1) of the Aashkol was 47.6% higher than the KP model (3.38 t h−1). Compared with the traditional system, across jute types, the Aashkol produced a 9% higher fiber yield and saved 46% retting time. Overall, the Aashkol reduced 90% of the labor requirement and saved 11.6 USD t−1 in jute fiber extraction and retting than the traditional method.

The present research was taken to formulate bacterial consortium as whole cell biocatalyst for retting of dry jute ribbons. The bacteria were obtained from different sources of jute retting water, enriched on nutrient broth medium. Microbial consortium was constructed from 7 (seven) selected isolated bacteria to become 7 (seven) combination culture which exhibited remarkable retting efficacy due to the induction of different enzymes activities. The enzymatic as well as biochemical activity of these bacteria were tested. The strains were selected based on the criteria that they were able to display good zone of inhibition. Formulations showed good potential as candidates for microbial consortium. In the two combination treatment with water (5 ml), microbial consortia of (10DTW2b+OMPW4b), (10DTW2b+4DTW7b) and (OMEW4b+10DTW2b) were found better for all the cases. Again, in three combinations treatment with water (5 ml d.H2O), fineness, brightness and smoothness/softness, all were found higher in microbial consortia of (3PRRF5b+4DTF1b+10DTW2b), which is a unique findings. This research is on-going and need to optimize these consortiums with different parameters and also carry out retting analysis.

La transizione ad un’economia bio-sostenibile ha previsto politicamente la coltivazione di biomassa per la produzione di energia e per quanto riguarda l’industria chimica l’impiego di materie prime rinnovabili in seguito al protocollo di Kyoto per far fronte ai cambiamenti climatici globali (UN FCCC, 1997). Fortunatamente, anche a livello industriale è stato riconosciuta l’importanza del concetto di “eco-efficienza” indispensabile per uno sviluppo sostenibile. Le fibre naturali di origine vegetale rappresentano la maggiore fonte di materia prima rinnovabile e potrebbero giocare un ruolo importante in questa transizione. La valenza economica del mercato di piante da fibra subì un calo dopo la Seconda Guerra Mondiale in seguito all’introduzione delle fibre sintetiche. Attualmente, la loro valenza ecologica ha implementato la ricerca e lo sviluppo di compositi contenti fibre rinforzate impiegate nell’industria dell’automobile, nella bio-edilizia e nella produzione di tessuti biodegradabili. Tuttavia, l’aumento della domanda di fibre naturali non ha ancora trovato un’offerta adeguata in grado di soddisfarla. Nell’ultimo decennio si è registrato un aumento della coltivazione delle piante da fibra come canapa, lino, kenaf e lino non supportate da uno sviluppo di un processo di estrazione delle fibre che ad oggi si basa ancora su sistemi tradizionali di macerazione. Il processo di separazione ed estrazione delle fibre dagli altri tessuti non fibrosi e dal midollo legnoso presenti nello stelo attraverso il distacco, la dissoluzione e la decomposizione delle pectine, gomme e le altre sostanze mucillaginose è chiamato retting. L’obbiettivo proncipale di questo studio, in collaborazione con K.E.F.I. S.p.a., è stato lo sviluppo del processo di estrazione delle fibre vegetali a livello industriale in bioreattore mediante ribbon retting del kenaf. Il lavoro sperimentale può essere diviso in tre parti: la prima parte ha riguardato l’ottimizzazione del processo di ribbon retting nel bioreattore analizzando diverse tipologie di materie prime (i ribbons di kenaf) e differenti varietà di kenaf (Everglade e Tainung); la seconda parte si è occupata di decifrare e caratterizzare la microflora che naturalmente si è sviluppata ed è stata coinvolta nella macerazione delle piante; la terza parte è servita ad identificare un possibile inoculo starter capace di implementare e standardizzare il processo di retting in bioreattore. Il processo di ribbon retting è un metodo particolare di macerzione basato sul pretrattamento meccanico degli steli che permette di ridurre: la quantità necessaria di acqua, il tempo di macerazione e l’inquinamento ambientale di circa un quarto in confronto agli altri metodi di macerazione che trattano lo stelo intero. In particolare, nella prima fase dello studio, le condizioni ottimali testate hanno permesso di garantire una miglior qualità di fibre di kenaf sia in termini di resistenza, finezza, colore e soprattutto hanno prodotto fibre libere da residui del midollo legnoso. L’ottimizzazione dei parametri di macerazione in bioreattore è stata condotta analizzando diversi carichi del bioreattore e testando differenti varietà di kenaf. La particolare impostazione del bioreattore, dotato di sistema di insufflazione di aria forzata ed di ricircolo del liquor di macerazione ha permesso di ottenere una macerazione spinta che ha prodotto in soli 5-7 giorni fibre di ottima qualità e perfettamente macerate. In particolare, la macerazione in bioreattore ha permesso di monitorare e controllare i principali parametri del processo (pH, RedOx, ossigeno disciolto e temperatura). Particolarmente utile si è dimostrata la regolazione dell’insufflazione dell’aria che ha permesso di mantenere il pH del liquor a livelli vicini alla neutralità evitando l’eccessiva acidificazione ed il rischio di over-retting con conseguente danneggiamento delle fibre di cellulosa, principali costituenti delle fibre vegetali. L’analisi microbiologica del liquor di macerazione mediante conta su diversi terreni di crescita ha evidenziato che durante il processo di macerazione popolazioni microbiche con attività pectinolitica si sono sviluppate sin dalle prime fasi del processo e hanno preso il sopravvento sull’iniziale microflora eterotrofa derivante dalla contaminazione naturalmente presente sugli steli delle piante e nell’acqua impiegata per la macerazione. L’analisi del liquido di macerazione ha evidenziato il rilascio di sostanze fenoliche probabilmente originatesi dalla lignina presente nei tessuti vegetali, che tuttavia si è stabilizzato nel corso della macerazione a valori che dipendevano dalla tipologia di kenaf e dal carico del bioreattore. Nella seconda fase lo studio della microflora batterica coinvolta nel processo di macerazione è stato condotto sul liquor attraverso due approcci differenti ma complementari: un approccio culture dependent ed un approccio culture independent. Durante lo studio microbiologico del liquor mediante l’approccio culture dependent, lo screening degli isolati pectinolitici mediante la tecnica A.R.D.R.A. ha evidenziato che la maggior parte degli isolati appartenga al genere Bacillus ed al gruppo dei gamma-Proteobacteria. L’approccio culture dependent mediante analisi D.G.G.E. condotta sulla regione ipervariabile V3 del gene 16S rDNA degli Eubatteri ha permesso l’individuazione della quasi totalità delle specie batteriche presenti nel liquor ed ha confermato la presenza di tali specie. In seguito, tra i batteri pectinolitici isolati dal liquor sono stati individuati 5 ceppi con spiccata attività pectinolitica: K2H1 B. pumilus, K2H2 B. subtilis, K2H3 B. pumilus, K2H7 B. licheniformis e K607 Enterobacter sp.. La maggiorparte degli isolati con spiccata attività pectinolitica appartiene a batteri sporigeni conosciuti in letteratura per la produzione di enzimi pectinolitici. Il saggio RDA con acido tannico ha dimostrato che tra gli isolati K607 Enterobacter sp non viene influenzato nella crescita dalla presenza di tali sostanze. La presenza di Enterobacteriaceae è stata riscontrata anche nelle acque reflue delle industrie cartarie suggerendo che questo ceppo possa essere legato alla regolazione del contenuto di sostanze fenoliche nel liquor. Nella terza fase, testando le capacità tecnologiche dei singoli ceppi pectinolitici in prove di macerazione in mesocosmo, è emerso che il ceppo K2H1 B. pumilus ha ottenuto i migliori risultati paragonabili a quelli ottenuti in bioreattore e, considerando le condizioni stringenti del mesocosmo, è possibile prospettare che l’inoculo massivo di tale ceppo possa accelerare la macerazione in bioreattore riducendo il tempo di macerazione senza comprometterne la qualità. Successivamente, dall’analisi proteomica degli enzimi pectinolitici prodotti e dall’attività enzimatica registrata durante la macerazione in mesocosmo dell’isolato K2H1 B. pumilus è emerso che l’attività pectinolitica principale è imputabile ad un esoenzima pectato liasi di tipo C che viene prodotto in elevate quantità dal batterio quando indotto dalla pectina. La pectato liasi agisce sulla catena dell’acido poligalatturonico che è il principale costituente della pectina solubilizzandola in molecole più piccole. Riassumendo, in questo studio è stato approntato un bioreattore su scala pilota in grado di estrarre in termini di quantità e qualità fibre vegetali di kenaf su scala industriale. Inoltre, il processo in bioreattore si è dimostrato un ambiente ideale per la ricerca e lo sviluppo del processo di macerazione mediante la caratterizzazione della microflora macerante e l’individuazione di un inoculo starter. In futuro, la sperimentazione dell’inoculo potrebbe ridurre i tempi di macerazione dai 5-7 giorni alle 48-72 ore. Inoltre, ulteriori studi delle proprietà enzimatiche dei batteri coinvolti nel processo di macerazione potrebbe permetter di implementare un processo enzimatico con ulteriori vantaggi in termini economici.
Transition to a more sustainable bio-based economy, as a political consequence of the Kyoto protocol on global climate change (United Nations Framework Convention on Climate Change, 1997), includes a shift of feedstock for energy and chemical industries from petrochemical to renewable resources. It is a good sign that also industries have by now recognized that the concept of "eco-efficiency" is an important way for businesses to contribute to sustainable development. As a major renewable resource lignocellulosic fibers derived from the structural plant tissues will play an important role in this transition. The markets for fiber crops such as flax, hemp, jute and sisal have seen substantial erosion since the introduction of synthetic fibers after Second World War in textile industries. Actually, the ecological 'green' image of cellulosic fibers has been the driving argument for innovation and development of products in the past decade, such as fiber reinforced composites in automotive industries, building and construction materials, biodegradable geotextiles and horticultural products. But today the industrial demand of natural fiber didn’t encountered yet an adequate offer able to soddisfying it. In fact, intensive cultivation of bast fiber crops as hemp, flax, kenaf and jute raised up while stalk processing for the extraction of bast fibers – the raw material for the industry - relied on traditional method of retting. The process of separation and extraction of fibers from non-fibrous tissues and woody part of the stem through separation, dissolution and decomposition of pectins, gums and other mucilaginous substances is called retting. The quality of the fiber is largely determined by the efficiency of the retting process. In retting, the most important aspect is that pectic materials are broken down and the fibers are liberated. Fiber quality is dependent on method of extraction applied in different natural conditions and duration of retting. The major aim of this study, in collaboration with K.E.F.I. S.p.a., was to develop a ribbon retting process in bioreactor in order to improve the extraction of bast fiber from kenaf plant to industrial scale. This study could be divided in three parts: the first part comprised the optimization of retting process in bioreactor by analyzing different kind raw materials (kenaf ribbons) and different variety of kenaf (Everglade and Tainung); in the second part the occurring bacterial microflora involved in plant maceration was deciphered and characterized; and in the third part a possible starter inoculum was identified in order to improve and standardize the retting process in bioreactor. Ribbon retting is a particular method of retting based on a mechanical pretreatment of plant stalks that allowed reducing: the requirement of water, the length of retting time and the level of environmental pollution to almost one-fourth in comparison to other method that processed the whole plant. In particular, in the first part of this study, the optimal tested conditions allowed assuring better quality kenaf fiber in terms of fiber strength, fineness, color, and overall absolutely barking free kenaf fiber. The optimization of main parameters of maceration in bioreactor was achieved analyzing different loadings of kenaf ribbons and different varieties of kenaf. The pilot plant was provided with air insufflation system and a retting liquor recycling apparatus which allowed processing perfectly kenaf ribbons in only 5-7 days. In particular, main parameters of bioreactor (pH, RedOx, oxygen content and temperature) were monitored and controlled during the process. The air insufflation system was very useful because controlled the excessive acidification of the liquor preventing over –retting risk with consequent damaging of cellulose (principal bast fibers component). Microbiological analysis of retting liquor by enumerating on different culture media evidenced the development of pectinolytic bacteria versus heterotrophic bacterial populations occurring on plant stem and in water. Moreover, the analysis of retting liquor evidenced the solubilization of phenolic compounds during maceration probably originating from lignin present in plant tissues. However, the phenolic content registered in retting liquor stabilized - during the process - to values influenced only by the loading of kenaf ribbons and kenaf varieties. The presence of phenolic compounds influenced negatively the development of bacterial populations by limiting the growth but also by inhibiting the enzymatic activities involved in the retting process. In the second part of this work, the study of the bacterial populations responsible of the retting process was achieved in retting liquor by two distinct but complementary approaches: culture dependent and independent approaches. During culture dependent approach and after screening of pectinolytic isolates through A.R.D.R.A. technique, strains belonging prevalently to genera Bacillus and gamma-Proteobacteria were identified. On the other side, culture independent approach such as D.G.G.E. analysis conducted on hypervariable V3 region of 16S rDNA of Eubacterial species confirmed the presence of those species. Later on, five high pectinolytic bacteria were isolated among strains isolated from retting liquor: K2H1 B. pumilus, K2H2 B. subtilis, K2H3 B. pumilus, K2H7 B. licheniformis e K607 Enterobacter sp.. Most of high pectinolytic strains belonged to spore-formers bacteria which are well known in literature to produce pectinolytic esoenzymes. On the other hand, RDA assay with tannic acid revealed that high pectinolytic isolates belonging to spore-formers bacteria were susceptible to phenolic compounds that inhibited their growth. Differently, K607 Enterobacter sp.’s growth was not affected by phenolic compounds. The presence of Enterobacteriaceae was normally encountered in wastewaters of pulp and paper industry suggesting that K607 Enterobacter sp. could be involved in the regulation of phenolic compounds content in retting liquor during the maceration. In the third part of this study, the five high pectinolytic strains were tested as massive inoculum for trial of maceration in mesocosms in order to identify a possible starter strain able to improve retting process in bioreactor. From the data obtained from trials of retting in mesocosms it was evident that K2H1 B. pumilus produced the best retted fibers in comparison to other strains and retted fibers from bioreactor. The conditions of retting applied in mesocosms could be considered as the worst retting conditions possible in bioreactor (no aeration, no recycle of retting liquor). For these reasons, it is possible to predict that K2H1 B. pumilus added as massive inoculum could improve the retting in bioreactor by reducing the time of retting without compromising the quality of retted fibers. Later on, proteomic analyses of pectinolytic enzymes produced by K2H1 B. pumilus evidenced that this strain when induced by pectin produce a pectate lyase type C. Pectate lyase acts preferentially on polygalacturonic acid that was the main component of pectin backbone, consequently pectin was disrupted in small soluble molecules. Summarizing, in this study a pilot plant bioreactor was built up able to extract bast fibers of kenaf at industrial level both in term of quality and quantity. Furthermore, the environment of bioreactor was suitable to develop the retting process and to study and characterize the bacterial populations that allowed isolating a starter inoculum. In the next future, the test of K2H1 B. pumilus as massive inoculum could improve the maceration by reducing time of retting from 5-7 days to 48-72 hours. Moreover, further studies on enzymatic activities of bacteria involved in retting of bast fiber crops could developed an enzymatic retting procedd that will be able to reduce time of retting from 48-72 hours to few hours.