Sayuri Akuzawa

Characterization of pullulanase (PUL)-deficient mutants of rice (Oryza sativa L.) and the function of PUL on starch biosynthesis in the developing rice endosperm

Rice (Oryza sativa) allelic sugary1 (sug1) mutants defective in isoamylase 1 (ISA1) accumulate varying levels of starch and phytoglycogen in their endosperm, and the activity of a pullulanase-type of a debranching enzyme (PUL) was found to correlate closely with the severity of the sug1 phenotype. Thus, three PUL-deficient mutants were generated to investigate the function of PUL in starch biosynthesis. The reduction of PUL activity had no pleiotropic effects on the other enzymes involved in starch biosynthesis. The short chains (DP ≤13) of amylopectin in PUL mutants were increased compared with that of the wild type, but the extent of the changes was much smaller than that of sug1 mutants. The α-glucan composition [amylose, amylopectin, water-soluble polysaccharide (WSP)] and the structure of the starch components (amylose and amylopectin) of the PUL mutants were essentially the same, although the average chain length of the B2-3 chains of amylopectin in the PUL mutant was ∼3 residues longer than that of the wild type. The double mutants between the PUL-null and mild sug1 mutants still retained starch in the outer layer of endosperm tissue, while the amounts of WSP and short chains (DP ≤7) of amylopectin were higher than those of the sug1 mutant; this indicates that the PUL function partially overlaps with that of ISA1 and its deficiency has a much smaller effect on the synthesis of amylopectin than ISA1 deficiency and the variation of the sug1 phenotype is not significantly dependent on the PUL activities.

Spinnability of Starch Pastes

We have developed apparatus to assess spinnability that uses an impedance to prevent of electrolysis. The spinning distance and the stress confirmed by measurement of dial gauge. A total of 10 starch pastes was prepared from corn, sago, katakuri, sweet potato, kuzu, edible canna, cassava, Indian lotus root, bracken, and potato, at 2% and 4% concentrations. The spinning distance of each starch paste showed a dependence on the concentration and the tensile velocity. The strain at the point of maximum stress increased in all samples with increases in the tensile velocity. The spinning energy increased with increase in the tensile velocity, with a particularly large dependence on the tensile velocity of potato. Cluster analysis was done using the spinning property values of 4% starch pastes as the parameters, which showed a division at a distance of 20, yielding four clusters, with each cluster showing a distinctive spinning pattern.

Draft Genome Sequence of Paenibacillus amylolyticus Heshi-A3, Isolated from Fermented Rice Bran in a Japanese Fermented Seafood Dish

ABSTRACT Paenibacillus amylolyticus strain Heshi-A3 was isolated in Fukui prefecture, Japan, from fermented rice bran in Heshiko, a traditional dish that is produced by aging salted mackerel with fresh rice bran at an ambient temperature for around 7 months to over one year. Here, we report the draft genome sequence of Paenibacillus amylolyticus strain Heshi-A3.

Draft Genome Sequence of Oceanobacillus picturae Heshi-B3, Isolated from Fermented Rice Bran in a Traditional Japanese Seafood Dish

ABSTRACT Oceanobacillus picturae strain Heshi-B3 was isolated from rice bran in a traditional fermented seafood dish named Heshiko, which was produced in Fukui Prefecture in Japan. Here, we report the draft genome sequence of O. picturae strain Heshi B-3.

Rheological study on physical modification starches

Publisher Summary Starch is commonly used for cooking and food processing as a viscosity enhancer and viscosity stabilizer. In this application, starch is required to be viscostable, thermostable, colorless, and transparent. Although starch chemically combines with numerous materials to improve its chemical and physical properties, food applications are restricted by law. This chapter examines some physical modifications to starch to obtain basic data for controlling the rheological properties of starch and starch paste. The physical modifications are done to incorporate several free fatty acids into starch and heat-moisture treated starch. The thermal properties and viscoelastic behavior are investigated for the effects of added free fatty acids on their properties of starch granules. The most obvious effect caused by the heat-moisture treatment is found to be an alteration of the structure of the elementary cell, resulting in the gelatinization properties and rheological properties of these pastes being dynamically changed. The concentration dependence of the mechanical properties of starch pastes near the sol–gel transition point is analyzed by the scaling law derived from the percolation theory.

Physical Properties of Starch Pastes

Starch paste is used in cooking and processing as a viscosity enhancer and viscosity stabilizer.1,2 But few studies have been conducted on its spinnability, which is a visco-elastic phenomenon. We have jointly developed a Rheoner RE-33005 with Yamaden Co.3 to assess spinnability. The area of the tip of the rod in this equipment is a very small cross-sectional area to minimize the effects of surface tension. The spinnability of various starch pastes was compared with this apparatus, and the results suggest that the characteristics of spinnability are important indicators of viscoelastic behavior. The relationship between spinnability and dynamic viscoelasticity was developed, and the stress relaxation was investigated.