Abstract
The overall kinetics of retting, a spontaneous fermentation of cassava roots performed in central Africa, was investigated in terms of microbial-population evolution and biochemical and physicochemical parameters. During the traditional process, endogenous cyanogens were almost totally degraded, plant cell walls were lysed by the simultaneous action of pectin methylesterase and pectate lyase, and organic acids (C(inf2) to C(inf4)) were produced. Most microorganisms identified were found to be facultative anaerobes which used the sugars (sucrose, glucose, and fructose) present in the roots as carbon sources. After 24 h of retting, the fermentation reached an equilibrium that was reproducible in all the spontaneous fermentations studied. Lactic acid bacteria were largely predominant (over 99% of the total flora after 48 h) and governed the fermentation. The epiphytic flora was first replaced by Lactococcus lactis, then by Leuconostoc mesenteroides, and finally, at the end of the process, by Lactobacillus plantarum. These organisms produced ethanol and high concentrations of lactate, which strongly acidified the retting juice. In addition, the rapid decrease in partial oxygen pressure rendered the process anaerobic. Strict anaerobes, such as Clostridium spp., developed and produced the volatile fatty acids (mainly butyrate) responsible, together with lactate, for the typical flavor of retted cassava. Yeasts (mostly Candida spp.) did not seem to play a significant role in the process, but their increasing numbers in the last stage of the process might influence the flavor and the preservation of the end products.
Full Text
The Full Text of this article is available as a PDF (191.8 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bensadoun A., Weinstein D. Assay of proteins in the presence of interfering materials. Anal Biochem. 1976 Jan;70(1):241–250. doi: 10.1016/s0003-2697(76)80064-4. [DOI] [PubMed] [Google Scholar]
- Crabbendam P. M., Neijssel O. M., Tempest D. W. Metabolic and energetic aspects of the growth of Clostridium butyricum on glucose in chemostat culture. Arch Microbiol. 1985 Sep;142(4):375–382. doi: 10.1007/BF00491907. [DOI] [PubMed] [Google Scholar]
- Gililland J. R., Vaughn R. H. Characteristics of Butyric Acid Bacteria from Olives. J Bacteriol. 1943 Oct;46(4):315–322. doi: 10.1128/jb.46.4.315-322.1943. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hósel W., Barz W. Beta-Glucosidases from Cicer arietinum L. Purification and Properties of isoflavone-7-O-glucoside-specific beta-glucosidases. Eur J Biochem. 1975 Sep 15;57(2):607–616. doi: 10.1111/j.1432-1033.1975.tb02336.x. [DOI] [PubMed] [Google Scholar]
- Macy J. M., Snellen J. E., Hungate R. E. Use of syringe methods for anaerobiosis. Am J Clin Nutr. 1972 Dec;25(12):1318–1323. doi: 10.1093/ajcn/25.12.1318. [DOI] [PubMed] [Google Scholar]
- Maduagwu E. N. Differential effects on the cyanogenic glycoside content of fermenting cassava root pulp by beta-glucosidase and microbial activities. Toxicol Lett. 1983 Mar;15(4):335–339. doi: 10.1016/0378-4274(83)90153-4. [DOI] [PubMed] [Google Scholar]
- McDonald L. C., Fleming H. P., Hassan H. M. Acid Tolerance of Leuconostoc mesenteroides and Lactobacillus plantarum. Appl Environ Microbiol. 1990 Jul;56(7):2120–2124. doi: 10.1128/aem.56.7.2120-2124.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mkpong O. E., Yan H., Chism G., Sayre R. T. Purification, characterization, and localization of linamarase in cassava. Plant Physiol. 1990 May;93(1):176–181. doi: 10.1104/pp.93.1.176. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Starr M. P., Chatterjee A. K., Starr P. B., Buchanan G. E. Enzymatic degradation of polygalacturonic acid by Yersinia and Klebsiella species in relation to clinical laboratory procedures. J Clin Microbiol. 1977 Oct;6(4):379–386. doi: 10.1128/jcm.6.4.379-386.1977. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Thompson J., Turner K. W., Thomas T. D. Catabolite inhibition and sequential metabolism of sugars by Streptococcus lactis. J Bacteriol. 1978 Mar;133(3):1163–1174. doi: 10.1128/jb.133.3.1163-1174.1978. [DOI] [PMC free article] [PubMed] [Google Scholar]