by Anita Das Ravindranath, S.Radhakrishnan, V.A.Sebastian and U.S.Sarma, Proceedings of the International workshop on Wet Processing of Coir, 8-9, December 1997

The mechanical extraction of  coir is an acceptable alternative to fibre production by conventional methods.  However, photo degradation and harsh  texture of mechanically extracted coir fibre are its limitations.  Treatment of the mechanically extracted fibre with COIRRET a bacterial cocktail has been observed to improve the light fastness of the fibre and improve the degree of softness for ease of spinning into coir yarn.  

“Coir” or coconut fibre is the source of raw material for the manufacture of exquisite floor coverings in the form of mate, mattings and carpets.  The advantage of coir is its natural origin which gives it an edge over synthetic fibres.  Coir fibre can be extracted from the coconut husk by retting in saline water or by defibering using machines.

  Retted fibre, extracted from coconut husks after steeping in saline water for 9-11 months, has a bright co lour which is consistent. Therefore, retted coir fibre is most suited for spinning of coir yarn for the manufacture of coir floor coverings.  However, retting has several disadvantages viz. a) it pollutes the backwaters  b) it is not economical  i.e. involves dead investment towards the cost of husk for 11 months and  c) involves drudgery of labor for steeping, drawing and beating of the retted husk.

  Coir fibre can be extracted through mechanical defibering by means of  crushing, defibering and combing machines.  The time required for the extraction of this fibre is only a few hours and the problem of polluting backwaters can be eliminated.  However, despite the advantage of yielding coir fibre in a short span of time, the greatest disadvantage of the mechanically extracted fibre is the inconsistent colour and harsh texture.

  Poor photo stability of coir fibre by photo degradation is one of the disadvantages for production of good coir yarn and products.

The biological method of bleaching or bleaching or “biobleaching” would be a desirable option to chemical bleaching on environmental considerations.  A literature survey conducted on “biobleaching” revealed that studies have been conducted on “biobleaching” of jute where is site growth of selected ligninolytic white rot fungus Polyporus sanguineus  on raw jute and gray fabrics was found to improve the light fastness on the samples.  Die ammonium phosphate treatment showed rapid multiplication of microorganisms within 72 hours and the resultant fibres used in sacking weft were found to have an appreciable improved quality ratio.  An alkaliphilic Bacillus sp. Strain  41 M-1 isolated from soil produced multiple xylanases extra cellularly. Xylanase J acted neither on the crystalline cellulose nor carboxymethyl cellulose indicating a possible application of the enzyme in biobleaching process.

This paper reports the findings of a study on the analysis of lignins in the coir fibre and application of COIRRET a bacterial preparation for biobleaching of coir using specific strains of phenol tic cultures.  The economics of the treatment in a commercial scale and its advantages to the coir industry are also discussed.

Materials & Methods

  a)  MAGTERIALS

1. One tone of decorticated coir fibre
2. COIRRET : The microorganisms constituting COIRRET belong to the Family Actinomycetes.  They are gram negative cells 0.1 to 0.5 micrometers wide and 1.25 to 4.5 micrometers long.  The cells are motile by means of subpolar tufts of flagella and possess the property of utilisation of 0.01% to 0..5% of phenolic compounds.
3. Nutrient Medium  prepared with beef extract, peptone and sodium chloride in 3 liter culture flasks and sterilized at 121 degrees for 20 minutes. The media was inoculated with 2 ml. of the COIRRET stock containing 210 X 4⁴ cells per ml. and incubated at 37 degrees for 7 days. The full grown biomass was used for the treatment of coir fibre @ 6kgs. Per metric tone.

  METHODS:-

  ESTIMATION OF LIGNIN IN COIR FIBRE FROM DIFFERENT REGIONS

Approximately one gram of finely out fibre was weighed  out in triplicate in  weighing bottles (previously tared )and dried at 105 degrees for one hour.  The material was weighed thrice till a constant weight (X)  was obtained.  The  material was then carefully transferred to a clean filter paper and   rolled to pack the   contents.  The  three packed samples were transferred into the reflux unit of the Soxhlet extraction apparatus for  the first extraction with ethanol :  benzene  (2:1 v/v) for the samples were then allowed to ;dry and the contents transferred to a 400 ml beaker  and refluxed in 200ml distilled water for 4 hours.  The cooled  samples  were then filtered   and air dried.   The  dried samples were then transferred into a 100 ml beaker to which was carefully added 3 ml of 72% sulphuric acid with the help of a glass rod.  Another  22 ml of 72% H2SO4 was added to make the total volume 25 ml.  The  sample was then carefully macerated to form a fine paste and kept covered at room temperature for 2  hours.  The sample  was then diluted with distilled water (575ml) in a one liter beaker and heated on a water bath for 4 hours .  After cooling the  sample was filtered carefully through a clean tared G scientered Gooch crucible. The residue was washed till free from acid, dried at 105 degrees and weighed till constant reading ob-Xtained. The net weight (Y) was recorded and the % lignin calculated.

ATTEMPTS OF IDENTIFICATION OF PHENOLIC COMPOUNDS IN RET LIQUOR

The presence of phenolic compounds in ret liquor was analysed using the Thin Layer Chromatography and paper chromatography.  The standard compounds resorcinol, catechol and pyrogallic acid were spotted along with the samples of ret liquor.  The solvent systems consisted of Benzene : Ethyl Acetate : Acetic Acid (85: 15: 1), Benzene : Dioxane : Acetic Acid ( 90: 25: 4) and Benzene : Methanol : Acetic Acid (48: 8: 4).  The spraying agent applied was tetrazotised benzidine.

The presence of phenolic compounds as the major constituents of coir ret water could be confirmed by analysis on the H.P.L.C using a C-8 5 mu Viosfer column.   The mobile phase was run isocratically with Water: Acetonitrile (80: 20) maintaining a flow rate of 0.5 ml. per minute.  The detector was set at a wavelength of 280 nm. In the U.V.range (Table I)

  TREATMENT OF MECHANICALLY EXTRACTED FIBRE WITH COIRRET

An industrial scale treatment of 100 bundles of unretted green husk fibre totaling to approximately 3000 kg.of fibre was carried out.  The treatment was conducted in a concrete tank with facilities for flushing of water into and out of the tank.  The bacterial consortia used for the treatment purpose was “COIRRET”.  The inoculums was prepared in 20 litres of medium and incubated for 10 days.  The fully grown bacterial biomass was seeded into the soak tank, twelve hours after soaking of the fibre. The study was monitored daily and samples of fibre drawn out for observation.  The water from the tank was drained out after forty eight hours of soaking and refilled and 10 bundles of fibre drawn out.  The fibre was subjected to spinning and the coir yarn samples were tested for light fastness rating using a Xenotest machine available at the Institute.  The test results are furnished in Table II

TEST METHOD: Exposure to Xenon Arc Lamp Quarzlampen Gessllschaft

M.B.M. Hanau FRG. Light and Dark Method

Humidity           : 70 %

Temperature   : 37 degrees

Test                  : 1006 : 1955

*Grades were determined by comparing with the fading time of the gray scale

  standards

Assessment of softness of COIRRET treated fibre using the Flexural Rigidity Tester

Fifty samples of each of treated and control fibre were tied up on a PVC rod to attain the form of a ring having a radius of 2.3 cms. And allowed to remain for 24 hours.  The rings were then tested on the Flexural Rigidity Tester with and without load and the deformation in loading determined.  The Flexural Rigidity was calculated using the following formula.

Flexural Rigidity            = 0.0047 mg. (2 Π r)²  cosø /tanø

Where mg                      = weight of load applied

                        r              = radius of the ring

                        d            = deformation of lower end of ring

                        ø            = 493d/2 Π r       

  Evaluation of Light fast ness

The light fastness test on the biobleached samples of coir was carried out on the Xeno test Equipment by exposure to Xenon Arc Lamp Quarzlampen Gesellschaft, M.B.H., Hanau FRG. Light and Dark Method.  The humidity was maintained at 70% and temperature at 37 degrees.  Details have been furnished in Table II.

The lignin content in coir fibre has been found to very between 34.52% to 39.39% depending upon the source of the fibre.  Biobleaching of coir is essentially partial delignification of the fibre and removal of a small percentage of surface lignins by biobleaching does not affect the strength of the coir fibre.

Evaluation of the colour, feel and light fastness of the treated samples revealed that the quality of the fibre treated with the strains of the bacterial cultures was improved considerably. The ratings were equivalent to that of the traditionally retted fibre.

The Flexural Rigidity of the treated sample is observed to be 0.157 gcm. As against the control sample which has a flexural rigidity of 0.602 gcm. Which indicates that the COIRRET treatment bestows a softer feel to the coir fibre.

The absorption spectrum is fingerprint for a specific compound and both the spectrum and specific column retention time can be determined by HPLC and compared to pure standards.  There were seven peaks observed in the coir ret liquor sample which was compared to the standard aromatic polyphenolic compouns.  The retention time at 2.75 minutes is close to that of the Ferulic acid, Vanillic acid and Pyrogallic acid.  The retention time at 3.525 can relate oto catechol, the peaks at 4.09, 5.65, 5.03 and 6.9 are yet to be identified.  It could be observed that hy immersing coir fibre/ coconut husks in water certain aromatic phenolic compounds such as those stated above are leached out into the water.  These compounds are photosensitive and tend to attain a darker colour when in contact with light and reabsorb on the surface of the fibre rendering the latter with a darker and duller shade.  By inoculation of strains of microbial cultures capable of degradation of the aromatic compounds leached out during retting of coir leads to their removal.  The reabsorption of the phenolics is avoided leading to the production of a fibre of brighter shade and improved quality.

The economics of treatment of coir with COIRRET  has also been worked out and 9the expenditure towards the treatment of coir fibre with COIRRET works out at Rs.0.62 per kilogram of fibre as per the costing worksheet detailed in TABLE I-III

BASIS : One Metric Tonne ( 1000 Kg)

i.e.   Rs.0.62 per kilogram of fibre  

Treatment of coir fibre with selected strains of bacterial cultures capable of degrading aromatic compounds which are phenolic in nature yielded a fibre exhibiting a higher degree of light fastness and a softer feel which is advantageous  to women spinners.

Therefore the study has indicated that biobleaching of coir using selective strains of microorganisms is an environment friendly and natural process that can be applied for yielding superior quality fibre for the production of good quality coir products.

The authors express their gratitude to Dr.A.K.Mukherjee, National Consultant Chemist for his guidance in the analysis of coir fibre and for assessment of its softness.   Acknowledgements are also due to the F.A.O for providing the analytical equipments for the studies carried out in this paper.

1.Annual Report 1984-85 Indian Jute Industries Research Association pp.63-64

2.Mohiuddin Ghulam Upgrading of Low Grade Jute and Cutlings Part I: Microbial

   Activity and its Enhancement by using Chemicals- J.Text. Institute 1992, 83 No.4

3.Satoshi Nakamura, Kenji Wakabayashi, Ryuichiro NAKAI. Purification and Some 

   properties of an alkaline Xylanase from Alkaliphilic Bacillus sp.strain 41-M-!.

   Applied and Environmental Microbiology, July 1993-P 2311-2316 Vol 56 No.7.