Production of chitin from shrimp biomaterials by lactic acid fermentation | |
| Author | Rao, Mukku Shrinivas |
| Call Number | AIT Diss. no.BP-00-02 |
| Subject(s) | Chitin Chitosan Shrimps Biomedical materials |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. BP-00-02 |
| Abstract | Shrimp is a magor fish food product in the world. About 40-50% of the whole shrimp is considered as waste. Crude shrimp biowaste contains 10-20% calcium, 30-45% protein and 8-10% chitin. Quality requirements for various applications of chitin and its derivative chitosan are different. This variance in the required quality standards for various applications also affects the process selection to produce chitin or chitosan. Conventionally, shrimp biowaste fractionation is carried out by soaking the shrimp waste in dilute solution of sodium hydroxide(= 4% NaOH) at 70-90 C and 4% hydrochloric acid. The main concern of this method is the high quantity of alkali and acid solution being used, which turns into highly corrosive waste and cannot be released without further treatment. Fractionation after partial fermentation using lactic acid bacteria has emerged to be an attractive alternative to the chemical process. A strain (Laclobacillus. Planiarum 541) was selected on basis of highest growth rate by plate counting method. The selected strain was further tested to determine optimum conditions of temperature, agitation, acid tolerance, initial pH and medium composition. Since the pH of shrimp waste is very high, high acidification rate is necessary. This can achieved by the acids produced by the microorganism. An optimum temperature of 30 C, with partial agitation was found to be one of the most important criteria. Besides, an initial pH between 5.5-6.25 was considered to be best condition for maximum growth and acidification. The strain appeared not to be acid tolerant. As an alternative to MRS medium, a medium having similar composition as MRS, but with commercial ingredients is recommended. After selecting the strain, the factors affecting the fermentation process have been identified and its econnomic viability studied. The quantity of Lactobacillus inoculum to be added, choice of carbon source, fermentation time, pH of shrimp at the start and during fermentation, temperature control during fermentation and the interval or speed of mixing, were found to influence the process. Important factors in the shrimp fermentation process are the medium conditioning by Lactobacillus through production of proteases and lowering the pH of the feermentation liquor. The efficiency of fermentation could be further improved by addition of different quantities and types of acids and by controlling pH initially and or during fermentation. The effect of meduim conditioning and addition of acid, separately and in combination, on storability, deproteination and demineralization of shrimp biowaste is reported. Addition of glucose supports the growth of lactic acid bacteria and therefore leads to better fermentation. Among the acids tested to control pH at the start during fermentation, acetic acid and citric acid have shown to be more efficient. In biowaste fermented with 6.7% L. plantarum inculum, 5% glucose and pH 6.0 adjusted with acetic acid, 75% deproteination and 86% demineralization was achieved. Replacement of acetic acid by citric acid gave 88% deproteination and 90% demineralization but poor product quality. The fermentation carried out in presence of acetic acid resulted in a good smelling protein fraction and a clean chitin fraction. To explore possibilities of using salt during fermentation, experiments have been conducted to determine the effect of salt concentration as high as 4%. Subsequently, a factorial design was constructed to study the combined effect of initial pH and NaCl concentration between 0-5% for both the strains. Empirical equations were obtained, which inferred that pH was the dominating factor in the growth of both strains, more than the effect of salt concentrations on growth. Tests on fermentation of shrimp waste with salt have revealed that 0-6% salt did not influence the fermentation and is not enough to replace the acetic acid addition. Sopilage was observed in instances where acid was not used to control the pH, with both the strains. It is observed that addition of protease enzyme to the lactic acid bacteria inoculum (Lactbacillus plantarum 541) gave higher defree of deproteination and decalcification when compared to only Lactobacillus or enzymatic treatment. 90% deproteination and more than 85% decalcification is obtained by using combination treatment of protease and Lactobacillus. The combination treatment not only utilizes the protease enzyme, which accelerates in detaching the protein from the shrimp, but also lactic acid bacteria create conditions of ensilation further decalcifying the waste. The 3L prototype reactor served as a good measure for studies on fermentation. Deproteination efficiency of 90% and demineralization efficiency of more than 85% was obtained with the use of the reactor. The 50L reactor was very efficient and good quality chitin and liquor was obtained. Separation of liquor and solid was easy and temperature and mixing control was achieved. Production of chitin from shrimp biowaste using Lactobacillus fermentation is a promising technique and could be commercialized. Constraints in inoculum management, maintaining clean conditions on a large scale, reducing medium costs and processing of liquor could make this environmental friendly technology the alternative of the future. |
| Year | 2000 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. BP-00-02 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Bioprocess Technology (BP) |
| Chairperson(s) | Steven, Willem F.; |
| Examination Committee(s) | Suwalee Chandrkrachang;Athapol Noomhorm;Rakshit, Sudip K.;Pakorn Nuchnoi;Guyot, Jean-Pierre; |
| Scholarship Donor(s) | Asian Institute of Technology; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2000 |