Year: 2007
Type: dissertation
Abstract: The present study aimed at the utlisation of microbial organisms for the\nproduction of good quality chitin and chitosan. The three strains used for the\nstudy were Lactobacillus plantarum, Lactobacililus brevis and Bacillus subtilis.\nThese strains were selected on the basis of their acid producing ability to reduce\nthe pH of the fermenting substrates to prevent spoilage and thus caused\ndemineralisation of the shell. Besides, the proteolytic enzymes in these strains\nacted on proteinaceous covering of shrimp and thus caused deprotenisation of\nshrimp shell waste. Thus the two processes involved in chitin production can be\naffected to certain extent using bacterial fermentation of shrimp shell.Optimization parameters like fermentation period, quantity of inoculum,\ntype of sugar, concentration of sugar etc. for fermentation with three different\nstrains were studied. For these, parameters like pH, Total titrable acidity (TTA),\nchanges in sugar concentration, changes in microbial count, sensory changes\netc. were studied.Fermentation study with Lactobacillus plantarum was continued with 20%\nw/v jaggery broth for 15 days. The inoculum prepared yislded a cell\nconcentration of approximately 108 CFU/ml. In the present study, lactic acid and\ndilute hydrochloric acid were used for initial pH adjustment because; without\nadjusting the initial pH, it took more than 5 hours for the lactic acid bacteria to\nconvert glucose to lactic acid and during this delay spoilage occurred due to\nputrefying enzymes active at neutral or higher pH. During the fermentation study,\npH first decreased in correspondence with increase in TTA values. This showed\na clear indication of acid production by the strain. This trend continued till their\nproteolytic activity showed an increasing trend. When the available sugar source\nstarted depleting, proteolytic activity also decreased and pH increased. This was\nclearly reflected in the sensory evaluation results. Lactic acid treated samples\nshowed greater extent of demineralization and deprotenisation at the end of\nfermentation study than hydrochloric acid treated samples. It can be due to the\neffect of strong hydrochloric acid on the initial microbial count, which directly\naffects the fermentation process. At the end of fermentation, about 76.5% of ash was removed in lactic acid treated samples and 71.8% in hydrochloric acid\ntreated samples; 72.8% of proteins in lactic acid treated samples and 70.6% in\nhydrochloric acid treated samples.The residual protein and ash in the fermented residue were reduced to\npermissible limit by treatment with 0.8N HCI and 1M NaOH. Characteristics of\nchitin like chitin content, ash content, protein content, % of N- acetylation etc.\nwere studied. Quality characteristics like viscosity, degree of deacetylation and\nmolecular weight of chitosan prepared were also compared. The chitosan\nsamples prepared from lactic acid treated showed high viscosity than HCI treated\nsamples. But degree of deacetylation is more in HCI treated samples than lactic\nacid treated ones. Characteristics of protein liquor obtained like its biogenic\ncomposition, amino acid composition, total volatile base nitrogen, alpha amino\nnitrogen etc. also were studied to find out its suitability as animal feed\nsupplement.Optimization of fermentation parameters for Lactobacillus brevis\nfermentation study was also conducted and parameters were standardized. Then\ndetailed fermentation study was done in 20%wlv jaggery broth for 17 days. Also\nthe effect of two different acid treatments (mild HCI and lactic acid) used for initial\npH adjustment on chitin production were also studied. In this study also trend of\nchanges in pH. changes in sugar concentration ,microbial count changes were\nsimilar to Lactobacillus plantarum studies. At the end of fermentation, residual\nprotein in the samples were only 32.48% in HCI treated samples and 31.85% in\nlactic acid treated samples. The residual ash content was about 33.68% in HCI\ntreated ones and 32.52% in lactic acid treated ones. The fermented residue was\nconverted to chitin with good characteristics by treatment with 1.2MNaOH and\n1NHCI.Characteristics of chitin samples prepared were studied and extent of Nacetylation\nwas about 84% in HCI treated chitin and 85%in lactic acid treated\nones assessed from FTIR spectrum. Chitosan was prepared from these samples\nby usual chemical method and its extent of solubility, degree of deacetylation,\nviscosity and molecular weight etc were studied. The values of viscosity and\nmolecular weight of the samples prepared were comparatively less than the\nchitosan prepared by Lactobacillus plantarum fermentation. Characteristics of protein liquor obtained were analyzed to determine its quality and is suitability as\nanimal feed supplement.Another strain used for the study was Bacillus subtilis and fermentation\nwas carried out in 20%w/v jaggery broth for 15 days. It was found that Bacillus\nsubtilis was more efficient than other Lactobacillus species for deprotenisation\nand demineralization. This was mainly due to the difference in the proteolytic\nnature of the strains. About 84% of protein and 72% of ash were removed at the\nend of fermentation. Considering the statistical significance (P<O.05) in the\nextent of demineralization and deproteinisation, we have taken 0.8N HCI for the\ndemineralization study and 0.6M NaOH for deprotenisation study. Properties of\nchitin and chitosan prepared were analyzed and studied.
Authors: T. Sini, P.T. Mathew
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1552004842