Bacterial cellulose production by Gluconacetobacter entanii using pecan nutshell as carbon source and its chemical functionalization.

Pecan nutshell is an abundant waste with a high content of carbohydrates. According to its chemical composition, pecan nutshell could be used as carbon source for Gluconacetobacter entanii, a bacterium that produces cellulose with high purity and nanometric characteristics. Bacterial cellulose (BC) was obtained from a static culture medium using pecan nutshell as carbon source and saccharose as control. Results showed that the pecan nutshell could be used as carbon source for production of BC. The cellulose yield ranged around 2.816 ± 0.040 g/L for 28 days. The morphological, structural and chemical properties of the cellulose produced were similar to those reported for others BC. The spectroscopic characterization indicated the chemical functionalization of BC and the reduction of its crystallinity. The production of BC with G. entanii using pecan nutshell as carbon source, is the first report. The BC could have potential use in chemical functionalization and in the preparation of biocomposites.

Effect of pulsed ultrasound on the physicochemical characteristics and emulsifying properties of squid (Dosidicus gigas) mantle proteins.

Food technologists are always looking to improve the functional properties of proteins. In this sense, in last years ultrasound has been used to improve some functional properties. For this reason, and considering that jumbo squid is an important fishery in northwest Mexico, the purpose of this research was to determine the effect of pulsed ultrasound on the physicochemical characteristics and emulsifying properties of squid (Dosidicus gigas) mantle proteins. Pulsed ultrasound (20kHz, 20, and 40% amplitude) was applied for 30, 60, and 90s to a protein extract prepared from giant squid mantle causing an increase (p<0.05) in surface hydrophobicity (So) from 108.4±1.4 to 239.1±2.4 after application of pulsed ultrasound at 40% of amplitude for 90s. The electrophoretic profile and the total and reactive sulfhydryl contents were not affected (p⩾0.05) by the ultrasound treatment. The emulsifying ability of the protein solution was improved (p<0.05), whereas the Emulsifier Activity Index (EAI) varied from123.67±5.52m2/g for the control and increased up to 217.7±3.8m2/g after application of the ultrasound. The Stability Emulsifier Index (EEI) was improved at 40% of amplitude by 60 and 90s. The results suggested that pulsed ultrasound used as pretreatment induced conformational changes in giant squid proteins, which improved the interfacial association between protein-oil phases, thus contributing to the improvement of their emulsifient properties.

Methods to obtain protein concentrates from jumbo squid (Dosidicus gigas) and evaluation of their functionality.

Jumbo squid is an important fishery resource in Mexico, and its muscle is lean and white and it has a very low price in the market. It is abundant, but with little or nothing added value, therefore is necessary to search alternatives of processing. Due to muscle characteristics, the aim of this study was to obtain protein concentrates using different methods. They were obtained by means of acidic (acid protein concentrates) and alkaline (alkaline protein concentrates) dissolution. Moreover, a protein concentrate was obtained by direct isoelectric precipitation and by the traditional method (neutral protein concentrates). The yield with better results was alkaline protein concentrates (63.58 ± 1.8%). The gel hardness was significantly different (p < 0.05), especially for the alkaline protein concentrates. The acid protein concentrates, isoelectric precipitation and alkaline protein concentrates were better with regard to the neutral protein concentrates, concerning the emulsifying and foaming properties. The protein concentrates by means of alkaline dissolution gave a better gelling property, but all the processes had the potential to obtain protein with emulsifying and foaming properties.

Extruded films of blended chitosan, low density polyethylene and ethylene acrylic acid.

The obtaining of chitosan extruded films was possible by using low density polyethylene (LDPE) as a matrix polymer and ethylene-acrylic acid copolymer as an adhesive, in order to ensure adhesion in the interphase of the immiscible polymers. The obtained blend films were resistant; however, a reduction in the mechanical resistance was observed as chitosan concentration increased. The thermal stability of the films showed a certain grade of interaction between polymers as seen in FTIR spectra. The antifungal activity of the extruded films was assessed against Aspergillus niger and high inhibition percentages were observed, which may be mainly attributed to barrier properties of the extruded films and the limited oxygen availability, resulting in the inability of the fungi to grow. A low adherence of fungal spores to the material surface was observed, mainly in areas with chitosan clumps, which can serve as starting points for material degradation.

Isolation and properties of AMP deaminase from jumbo squid (Dosidicus gigas) mantle muscle from the Gulf of California, Mexico.

Adenosine monophosphate (AMP) deaminase was purified from jumbo squid mantle muscle by chromatography in cellulose phosphate, Q-Fast and 5'-AMP sepharose. Specific activity of 2.5U/mg protein, 4.5% recovery and 133.68 purification fold were obtained at the end of the experiment. SDS-PAGE showed a single band with 87kDa molecular mass, native PAGE proved a band of 178kDa, whereas gel filtration detected a 180kDa protein, suggesting the homodimeric nature of this enzyme, in which subunits are not linked by covalent forces. Isoelectric focusing of this enzyme showed a pI of 5.76, which agrees with pI values of AMP deaminase from other invertebrate organisms. AMP deaminase presented a kinetic sigmoidal plot with Vmax of 1.16µM/min/mg, Km of 13mM, Kcat of 3.48µM.s(-1) and a Kcat/Km of 267 (mol/L)(-1).s(-1). The apparent relative low catalytic activity of jumbo squid muscle AMP deaminase in the absence of positive effectors is similar to that reported for homologous enzymes in other invertebrate organisms.