Showing papers by "Central Tuber Crops Research Institute published in 2004"

Extracellular amylase(s) production by fungi Botryodiplodia theobromae and Rhizopus oryzae grown on cassava starch residue.

Abstract: The fungi Botryodiplodia theobromae and Rhizopus oryzae produce extracellular amylase when grown on a liquid medium containing 2% (WN) soluble starch or cassava starch residue(CSR) (as starch equivalent), a waste generated after extraction of starch from cassava, as the sole carbon source. Using CSR as the sole carbon source, the highest amylase activity of 3.25 and 3.8 units (mg, glucose released x ml(-1) x h(-1)) were obtained in shake flask cultures during the late stationary phase of growth of B. theobromae and R. oryzae, respectively. These values were slightly lower than the values obtained using soluble starch as the carbon source. Maximum enzyme synthesis in CSR incorporated medium occurred at the growth temperature of 30 degrees C and pH 6.0. Presence of inorganic NH4+ salts like ammonium acetate and ammonium nitrate in culture medium yielded more amylase than the other nitrogen sources. Amylase(s) production in the controlled environment of a Table-Top glass Jar Fermenter (2-L capacity) was 4.8 and 5.1 units for B. theobromae and R. oryzae, respectively using CSR as the carbon substrate. It is concluded that CSR, a cheap agricultural waste obtained after starch extraction from cassava could replace soluble starch as carbon substrate for commercial production of fungal amylase(s).

Purification and Partial Characterization of Proteinase and α-Amylase Inhibitors from Lesser Yam (Dioscorea esculenta)

Abstract: The proteinase and α-amylase isoinhibitors of lesser yam were isolated through TCA precipitation and DEAE cellulose chromatography. The major peak with proteinase inhibitor activity obtained by DEAE-cellulose chromatography was further fractionated to five isoinhibitor fractions with molecular weights 67, 50, 27, 15, and 12 kDa respectively in GPC and PAGE. On the contrary, the major peak with α-amylase inhibitor activity segregated into four isoinhibitors with molecular weights 63, 31, 24, and 16 kDa. Unlike most trypsin inhibitors the lesser yam proteinase inhibitors (LYTI) exhibited proportionate decrease in trypsin inhibition with increase in inhibitor concentration. The inhibitor potential of lesser yam α-amylase inhibitor (LYAI) however, increased with increase in inhibitor concentration. The LYTI was fairly thermostable, retaining 50% activity even after heating for 4 h at 90°C, while the LYAI was much less stable at this temperature. Out of the five fractions of LYTI, isoinhibitors II and...

Isozyme analysis of indigenous cassava germplasm for identification of duplicates

Abstract: Isozyme analysis was utilized for identification of duplicates in indigenous collection of cassava germplasm. 786 indigenous accessions of cassava were screened for 11 key morphological characters and the morphological duplicates were identified. Two hundred and eighteen accessions of cassava consisting of ninety one sets of morphological duplicates were analysed for esterase isozyme polymorphism. Thirty seven polymorphic bands were obtained, showing high polymorphism for this enzyme. Thirty seven double sets and 17 multiple sets were found to be similar at isozyme level. These isozyme duplicates will be further analysed for DNA similarity before eliminating them from the field germplasm. The dissimilar sets showed variation in minor morphological characters, thus confirming the relation between isozyme polymorphism and phenotypic variation.