Abstract The effect of short‐term storage on the protein, phosphorus and phenolic content as well as peroxidase and o ‐diphenolase activities of cut, harvested Jamaican yam ( Dioscorea sp) tubers ( D rotundata. D alata and D cayenensis ) was studied. There was an initial increase in the total phenolic content up to the third week of storage followed by a gradual decrease to the sixth week. Phenolic content was found to be highest in D cayenensis followed by D rotundata and D alata. The activities of peroxidase (EC 1. 11. 1. 7) and o ‐diphenolase (EC 1. 10.3.1) increased steadily up to the third week of storage and thereafter decreased to the fifth week. The intensity and rapidity of browning in tubers when cut, correlated very closely with the tuber o ‐diphenolase and phenolic content levels while the onset of rotting correlated with the peroxidase activity levels in the species studied.
Abstract Starch granules from Round leaf yellow yam, Negro yam, Sweet yam, Bitter yam and Chinese yam grown in Jamaica were isolated and characterized. The amylose content, granular size, crystallinity, and digestibility by α‐amylase were determined. The granules obtained were of three crystalline types. Round leaf yellow yam, Negro yam and Sweet yam were found to be type‐B, while Chinese yam and Bitter yam were type‐C and type‐A, respectively. Round leaf yellow yam had the highest amylose content (26.5%) while Chinese yam had the lowest (11.1%). The granule size varied between 1–3 μm for Chinese yam and 16–42 μm for Round leaf yellow yam. Significant variations in digestibility of the granules were observed. Raw starches from Chinese yam and Bitter yam were the most susceptible to α‐amylase digestion (porcine pancreatic α‐amylase, pH 5.5, 0.02% CaCl 2 , 40°C, 24 h) with 21.27 ± 0.01% and 18.11 ± 0.02% degradation, respectively, while Round leaf yellow yam, Negro yam and Sweet yam starches were the least susceptible, with 13.74 ± 0.03%, 14.98 ± 0.08%, and 15.32 ± 0.04% enzymatic degradation, respectively.
Enolase is a ubiquitous enzyme found in the glycolytic pathway of organisms of all three domains of life and is involved in the catalysis of the reversible conversion of 2-Phosphoglycerate (2PG) to Phosphoenolpyruvate (PEP). Enolase in Mycobacterium tuberculosis stands out from dimeric homologs by being catalytically active only in an octameric state. While the mechanism of forward reaction is well understood, not much is known about how does the catalytic conversion of PEP to 2PG take place. Here we present structural snapshots of M. tuberculosis enolase at various stages as it progresses through the reverse reaction. We found a plausible catalytic pathway involving a novel transient product bound state called ‘alternate conformation’, in addition to the canonical one. We observed two major deviations from the forward reaction: presence of MgB is non-obligatory for the reaction, and flipping of 2PG to an alternate conformation makes it energetically feasible to exit the active site. Molecular dynamics and binding free energy calculation studies further indicate that the alternate conformation may resemble an exit conformation by facilitating the opening of active site loops due to the distortion in metal ion coordination and H-bonding interactions. Along with a trajectory of breathing motions of the active site loops during the reaction and insight about conformational change of 2PG at the active site; this study provides the first high-resolution structural information about the reverse catalysis by the enolase.
Starch granules from round leaf yellow yam (RY), Lucea yam (LY), white yam (WY), and Chinese yam (CY) grown in Jamaica were isolated and the relationship between starch amylose content, crystallinity, microscopic properties, in vitro digestibility, and the glycemic index (GI) of the tubers was investigated. The results indicate that RY had the highest amylose content (265.30 +/- 0.09 g/kg starch) while CY the lowest (111.44 +/- 0.03 g/kg starch). A corresponding variation in starch digestibility and GI was also observed, as CY which had the highest in vitro digestibility had the highest GI (21.27 +/- 0.01 and 97.42 +/- 0.62%, respectively), while RY, LY, and WY starches with low digestibility had lowest GI. Differences in the crystalline pattern of the different starches were observed, where RY, LY, and WY displayed the type B crystalline pattern while CY had the intermediate crystallite (type C).
Both gram positive and gram negative bacteria were isolated from yam (Dioscorea spp) tubers obtained from Jamaica and Nigeria. The total bacterial count and species indicated that different types of bacteria exist to varying extents in different yam tubers. An intrinsic antibiotic resistance profile showed that up to 83% of the strains were resistant to ampicillin (50 ?g mL-1), but most were sensitive to streptomycin (15 ?g mL-1) and kanamycin (50 ?g mL-1). Fourteen of the endophytes contained plasmid deoxyribonucleic acid (DNA), seven of which possessed a single plasmid of 22 kb while the other seven had two plasmids of 22 kb and 38 kb. Bacterial isolates from D. rotundata cv. Ikale containing single and double plasmids were identified by fatty acid profiling as Pantoea dispersa belonging to the Erwinia-Pantoea complex. Endonuclease restriction showed the 22 kb plasmid from endogenous P. dispersa to possess multiple restriction sites for EcoRI, Pstl, BamHI, SalI, HincII, MluI, and SmaI. Their apparent non-pathogenic existence in the yam host and their genetic elements could be further explored for possible exploitation as vectors in the genetic engineering of yam.
The effect of foliar spray of young lemon trees with Chitosan (CH) (200 - 300 - 400 ppm), on antioxidant enzymes activities (peroxidase POD, polyphenol oxidase PPO) and total phenolic content, and their influence on leaf miner (Phyllocnistis citrella) activity (tunnel length and damage density) under field condition was investigated. The results showed that treatment with chitosan 300 ppm enhanced the total phenolic content (5.975 mg/g) and the POD activity (0.533 min-1 mg-1 protein), while PPO activity was increased by chitosan 200 ppm (1.394 ΔA/min/g FW). The results demonstrated as well that chitosan treatment has a beneficial effect in reducing leaf miner activity, by decreasing tunnel length and damage density.
Abstract In an attempt to identify appropriate feeding rates for multispecies of fish raised in fertilized earthen ponds, the present work was conducted over a 19-week experimental period to establish the growth performance, production and body composition of Nile tilapia, common carp and silver carp fed 0.0%, 0.5%, 1.0%, 3.0%, 5.0% biomass and to apparent satiation (treatments). Twelve ponds were stocked with a similar number and weight of each fish species. Two ponds were assigned to each of the treatments, and a 25% protein pelleted fish feed was used to feed fish at the specified rate of feeding. At the end of the experiment, growth, weight gain, survival, yield and body composition of fish groups were affected by the treatments. The economic effectiveness also varied among treatments. The most conspicuous attribute of the feeding rates was its lack of influence on growth (g day−1), weight gain (g per fish), yield (kg ha−1) or body composition of silver carp. The results of whole-body proximate analysis indicated that various feeding rates had either an irregular pattern or no effects on the protein and ash gain per 100 g of fish body weight (bw) gain. The most notable exceptions were significant (P < 0.05) increases in body fat and gross energy gains in Nile tilapia, common carp and silver carp accompanied by decreases in percentages of moisture (but not in silver carp) as feeding rate increased. Among the six different feeding levels, feeding to apparent satiation (feed amount was equivalent to 2.67% of fish bw day−1) appeared to be optimal, as it significantly (P < 0.05) supported the highest fish production, income and net profit compared with all other treatments except for the 3% feeding level, for which the differences in those measurements were comparable.
Abstract Dioscorea yam tubers of 11 cultivars from five common species grown in Jamaica were analysed for the following: protein content, total phenolics, vitamin C, total lipids, fatty acid composition and activity of the polyphenol oxidase enzyme. The results show that the yams grown in Jamaica are of good nutritional value with considerable amounts of protein, vitamin C, low lipids with only one cultivar ‘renta yam’ ( D alata ) possessing high levels of phenolic compounds. The fatty acids present in the total lipid extracts show that yam tubers generally possess high levels of saturated fatty acids mainly palmitic acid. However, the species D alata (cv white yam) and the species D trifida (cv yampie) have high levels of the unsaturated fatty acid, linolenic. All the polyphenol oxidases from the 11 cultivars show activities towards the diphenol substrates, catechol and DL‐DOPA (DL‐3,4‐dihydroxyphenylalanine). However, no oxidation was observed with L‐tyrosine, a monophenol substrate. All cultivars studied were found to have different lengths of dormancy which varied with storage conditions. When the harvested tubers were washed, sunned and stored at 20†C in a dark cupboard, it was possible to extend their lengths of dormancy by a further 11 weeks.
Abstract In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T‐I) (control treatment); 2) 6‐wk delay of feeding after fish stocking (T‐II); 3) 13‐wk delay of feeding after fish stocking (T‐III), and 4) no supplemental feed application (T‐IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T‐I, T‐II, and T‐III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T‐II showed weight gain, growth rates, and yields significantly higher than fish in T‐III or T‐IV. Also, the total fish production and net profit in T‐II were significantly higher than in T‐III or T‐IV. Fish species in T‐II showed weight gain, growth rates, survival rates, and yields similar to those of T‐I (control treatment) with no significant differences. The amount of feed consumed by fish in T‐II was reduced by approximately 7.3% compared to that consumed by fish at T‐I. Moreover, there was increase in th net profit in T‐II by 4.8% over that achieved in T‐I. Therefore, T‐II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)
