Physicochemical and protein characterization of lima bean (Phaseolus lunatus L) seed

Lima bean (Phaseolus lunatus L) is native to Latin America and has spread out worldwide, thus having a high level of diversity. The lima bean seed from a specific region might have different characteristics from others. This study was aimed to characterize the physicochemical and protein of the dry seed of lima bean from Indonesia based on its solubility, electrophoretic pattern, and amino acid profile. The result showed that carbohydrate (68.89±1.55%) was the major component, with starch (41.96±1.10%) as the predominant. The amylopectin was higher than amylose. Dietary fibre (27.87±0.37%) was significant and dominated by insoluble one (25.47±0.32%). The fat content (1.15±0.04%) was low and ash (3.67±0.47%) comprised of magnesium, phosphorus, potassium, calcium, and iron with the content of 184, 75, 38, 11, and 10 mg/100 g, respectively. Total phenolic compounds of this seed were 1.29±0.02 mg/g, phytic acid 11.57±0.03 mg/g, saponins 16.84±0.42 mg/g, and trypsin inhibitors 36.07±0.11 TIU/g. HCN was found significantly at 30.99±0.29 ppm. Oligosaccharides were 5.93±0.29% that comprised of raffinose 1.22±0.08% and stachyose 4.61±0.21%. Protein content was moderate (15.93±0.55%) that comprised of albumin 18.47±0.62%, globulin 56.20±2.00%, prolamin 3.14±0.20%, and glutelin 22.69±1.60%. The molecular weight of this protein was 10-141 kDa with 12 polypeptides. Globulin had 12 polypeptides of 10 to 124 kDa. Albumin had 18 to 116 kDa molecular weights, while glutelin had six polypeptides of 13 to 109 kDa. Prolamin did not have visible polypeptides. Lysine, leucine, valine, and phenylalanine were the primary essential amino acids with high lysine but low methionine and cysteine. In conclusion, lima bean seed is a source of carbohydrates and minerals, with a moderate protein content dominated by the globulin. The polypeptide profile of lima bean seed is varied depending on the protein fractions. The occurrence of antinutrition might hinder its utilization as a protein source. HCN as a toxicant should be removed to obtain a safe seed for consumption.

Physical properties and cooking quality of extruded restructured rice: impact of water temperature and water level

Rice is the main food for approximately 3.5 billion people worldwide, especially in Asians, who have consumed more than 90% of the total rice produced. Restructured rice is another designation of artificial rice is an effort to diversify staple foods processed from carbohydrate-based raw materials with the addition of certain substances to improve the quality of staple foods. Restructured rice can be done with several techniques, such as using extrusion. This study aimed to investigate the effect water content (35%, 37.5%, 40%, 42.5%, and 45%) and temperature (100oC and 26oC) on the surface and characteristics of restructured rice using a pasta extruder. Results of this study showed the treatment with water content 40% and temperature 100oC to be the best, more precisely seen from the results of laser microscope, color, WAI, WSI, WAR, Cooking losses, and cooking time. Pores and surfaces of restructured rice are almost the same as milled rice. Water absorption index (WAI) value = 2.273±0.10 g/g, WSI = 2.114±0.11%, WAR = 150.99±0.77%, CL = 1.92±0.10% and cooking time 4 mins. Suggestions for this research are further studies such as fortification with other ingredients using a pasta extruder technology and are expected to be implemented and commercialized.

A ratiometric NMR pH sensing strategy based on a slow-proton-exchange (SPE) mechanism

Real time and non-invasive detection of pH in live biological systems is crucial for understanding the physiological role of acid-base homeostasis and for detecting pathological conditions associated with pH imbalance. One method to achieve in vivo pH monitoring is NMR. Conventional NMR methods, however, mainly utilize molecular sensors displaying pH-dependent chemical shift changes, which are vulnerable to multiple pH-independent factors. Here, we present a novel ratiometric strategy for sensitive and accurate pH sensing based on a small synthetic molecule, SPE1, which exhibits exceptionally slow proton exchange on the NMR time scale. Each protonation state of the sensor displays distinct NMR signals and the ratio of these signals affords precise pH values. In contrast to standard NMR methods, this ratiometric mechanism is not based on a chemical shift change, and SPE1 binds protons with high selectivity, resulting in accurate measurements. SPE1 was used to measure the pH in a single oocyte as well as in bacterial cultures, demonstrating the versatility of this method and establishing the foundation for broad biological applications.

A chitinase with high activity toward partially N-acetylated chitosan from a new, moderately thermophilic, chitin-degrading bacterium, Ralstonia sp. A-471

A moderately thermophilic bacterium, strain A-471, capable of degrading chitin was isolated from a composting system of chitin-containing waste. Analysis of the 16S rDNA sequence revealed that the bacterium belongs to the genus Ralstonia. A thermostable chitinase A ( Ra-ChiA) was purified from culture fluid of the bacterium grown in colloidal chitin medium. Purification of the enzyme was achieved mainly by exploiting its binding to the colloidal chitin. The molecular mass of the enzyme was estimated to be 70 kDa and the isoelectric point approximately 4.7. N-terminal amino acid sequencing revealed a sequence of ADPYLKVAYYP, which had high homology (66% identity) with that of chitinase A1 from Bacillus circulans WL-12. The pH and temperature optima were determined to be 5.0 and 70 degrees C, respectively. The enzyme was classified as a retaining glycosyl hydrolase and was most active against partially N-acetylated chitosans. Its activities towards the partially N-acetylated chitosans, i.e. chitosan 7B, chitosan 8B, and chitosan 9B, were about 11-fold, 9-fold, and 5-fold higher than towards colloidal chitin, respectively. Ra-ChiA cleaved (GlcNAc)6 almost exclusively into (GlcNAc)2. Activation of Ra-ChiA was observed by the addition of 1 mM Cu2+, Mn2+, Ca2+, or Mg2+. Degradation of the partially N-acetylated chitosan produced oligosaccharides with a degree of polymerization ranging from 1-8; these are products that offer potential application for functional oligosaccharide production.

Expression of a gene encoding chitinase (pCA 8 ORF) from Aeromonas sp. no. 10S-24 in Escherichia coli and enzyme characterization

A gene encoding chitinase from Aeromonas sp. no. 10S-24 was expressed using pTrc99A in Escherichia coli JM 105 which yielded a 5-fold higher activity than when pUC19 was used. Three different truncated enzymes (SA-1, SA-2 and SA-3) were obtained after purification. Their isoelectric points were 7.0, 6.9, and 6.7, respectively. The enzymes showed two optimum pHs, 4.0 and 7.0, when incubated with ethylene glycol chitin as the substrate, and were stable over a wide pH range (3.0-9.0). The optimum temperature was 60 degrees C and the enzymes were stable up to 50 degrees C. The chitinases exhibited wide substrate specificities for chitin-related compounds.