Kenzo Shimahara

Preparation of crustacean chitin

Publisher Summary This chapter describes the isolation of chitin from crustacean cuticles (shells). To isolate chitin from crustacean shells, the following three steps are required: (1) demineralization with dilute hydrochloric acid or with ethylenediaminetetraacetic acid (EDTA), (2) deproteinization with aqueous sodium hydroxide or by use of the proteolytic activity of a bacterium, and (3) elimination of lipids with organic solvent(s). The chapter tabulates composition and molecular weight of various chitin preparations from abdominal shell of Penaeus japonicus (kuruma prawn). The chapter also describes the preparation of colloidal chitin. The procedure consists of the dissolution of chitin into and the reprecipitation from concentrated hydrochloric acid and the dispersion of the reprecipitated chitin into water. Colloidal chitin serves as a substrate of chitinase and a carbon and nitrogen source of chitinolytic microorganisms.

Peracetylated chitobiose: Preparation by specific degradations of chitin, and chemical manipulations

Abstract Chitobiose octaacetate (3) was preparable in moderate yield from chitin by microbial degradation followed by acetylation, or by modified chemical degradation. Compound 3 was chemically manipulated to give various compounds, including an oxazoline derivative, glycosides, and partially O-benzylated derivatives. The conformation of the oxazoline derivative is discussed.

CHEMICAL COMPOSITION AND SOME PROPERTIES OF CRUSTACEAN CHITIN PREPARED BY USE OF PROTEOLYTIC ACTIVITY OF PSEUDOMONAS MALTOPHILIA LC102

A proteolytic bacterium Pseudomonas maltophilia LC102 was cultured at 30 °C in a medium consisted of K 2 HPO 4 and Penaeus japonicus cuticle previously decalcified in 0.1 M EDTA solution at pH 7.5. Protein content of the cuticle decreased from initial 25.4% to 0.7% within 24 hr. After this period, the velocity of deproteinization diminished markedly and complete removal of the protein was not attained. Protein content of the cuticle from 7-day culture was 0.3%. Decalcified cuticles of other Decapoda species , Panulirus japonicus, Paralithodes camtschatecus, Chionoecetes opilio, and Porutunus trituber-culatus, were more slowly deproteinized. Their cuticles from 7-day cultures contained protein in the range from 3 to 5%.

Factors affecting the surviving fractions of resting Escherichia coli B and K-12 cells exposed to alternating current.

Resting Escherichia coli B and K-12 cells suspended in a phosphate buffer solution were exposed to alternating current (AC) of 50 Hz. The surviving fractions of cells exposed to AC were decreased with an increase in current density from 0 to 300mA/cm2 at 29±3°C for a definite exposure time. At a definite current density the fractions were decreased proportionally with exposure time. Even for conditions of definite exposure time and current density, the fractions varied depending on the concentration of cells initially suspended in buffer solution in AC-exposure chamber. E. coli cells were more resistant to AC-exposure under anaerobic conditions than aerobic conditions. Addition of catalase to the cell suspension during AC-exposure effectively protected both strains. Methionine and albumin had mild protective effects, but chemicals, such as cysteine, ehanol or α-tocopherol had little protective effect.

Decrease in High Pressure Tolerance of Resting Cells of Escherichia coli K-12 by Pretreatment with Alternating Current

The effects of 50 Hz alternating current (a.c.) pretreatment on the high pressure tolerance of Escherichia coli K-12 cells were found to be dependent on the composition of the solutions suspending the cells during treatment with pressure up to 4000 kg/cm2 at room temperature for 10min. When pressurized in a 8/15 m NaCl solution (pH 7.0) at 3000 kg/cm2 after a.c. exposure of 600mA/cm2 for 2 hr at 35°C, the exposed cells could not survive as well as those pressurized in a 8/15 m phosphate buffer (pH 7.0): the value of the ratio of the exposed cells surviving to that of the unexposed ones was less than 0.1 in an NaCl solution and about 0.5 in a buffer. The lethal action of high pressure on the cells suspended in m/15 buffer was appreciably counteracted by 8/15 m buffer but not by 8/15 m NaCl solution.

Application of powdered ceramics support to the production of l-tryptophan by resting Escherichia coli K-12 cells

Abstract Escherichia coli K-12 cells having tryptophanase activity could be readily adsorbed to the surface of commercial ceramic powders such as γ-alumina, silica, titania, zirconia or glass, when they were suspended in a neutral or alkaline buffer solution in the presence of poly(methacryl-oxyethyl trimethyl ammonium chloride) (PMAAC), a cationic flocculant. Tryptophanase activity of the cells treated with PMAAC was somewhat less than that of the untreated cells, however, the activity of the cells adsorbed to titania, zirconia or glass powder after five recyclings was appreciably more stable than that of the intact cells.