Structural characterization of chitin and chitosan obtained by biological and chemical methods

Chitin production was biologically achieved by lactic acid fermentation (LAF) of shrimp waste (Litopenaeus vannameii) in a packed bed column reactor with maximal percentages of demineralization (D(MIN)) and deproteinization (D(PROT)) after 96 h of 92 and 94%, respectively. This procedure also afforded high free astaxanthin recovery with up to 2400 μg per gram of silage. Chitin product was also obtained from the shrimp waste by a chemical method using acid and alkali for comparison. The biologically obtained chitin (BIO-C) showed higher M(w) (1200 kDa) and crystallinity index (I(CR)) (86%) than the chemically extracted chitin (CH-C). A multistep freeze-pump-thaw (FPT) methodology was applied to obtain medium M(w) chitosan (400 kDa) with degree of acetylation (DA) ca. 10% from BIO-C, which was higher than that from CH-C. Additionally, I(CR) values showed the preservation of crystalline chitin structure in BIO-C derivatives at low DA (40-25%). Moreover, the FPT deacetylation of the attained BIO-C produced chitosans with bloc copolymer structure inherited from a coarse chitin crystalline morphology. Therefore, our LAF method combined with FPT proved to be an affective biological method to avoid excessive depolymerization and loss of crystallinity during chitosan production, which offers new perspective applications for this material.

Selective enzyme-mediated extraction of capsaicinoids and caratenoids from chili guajillo puya (Capsicum annum L.) using ethanol as solvent

The selective extraction of capsaicinoids and carotenoids from chili guajillo "puya" flour was studied. When ethanol was used as solvent, 80% of capsaicinoids and 73% of carotenoids were extracted, representing an interesting alternative for the substitution of hexane in industrial processes. Additionally, when the flour was pretreated with enzymes that break the cell wall and then dried, extraction in ethanol increased to 11 and 7% for carotenoid and capsaicinoid, respectively. A selective two-stage extraction process after the treatment with enzymes is proposed. The first step uses 30% (v/v) ethanol and releases up to 60% of the initial capsaicinoids, and the second extraction step with industrial ethanol permits the recovery of 83% of carotenoids present in the flour.

Ultrasonication and steam-explosion as chitin pretreatments for chitin oligosaccharide production by chitinases of Lecanicillium lecanii

In this study, chitin oligosaccharides have been successfully produced using chitinases from submerged fermentation of Lecanicillium lecanii. The highest Hex, Chit and Prot production was 0.14, 0.26 and 2.05 U/mg of protein, respectively, which were attained varying pH from 5 to 8 after 96 h. Culture conditions conducted at constant pH of 6 resulted in significantly lower enzyme production. The crude enzyme was partially purified by salting out with (NH4)2SO4 followed by size exclusion chromatography to isolate the chitinase mixture for further chitin hydrolysis assays. In this regard, chitin substrates were pretreated with sonication and steam explosion prior to enzymatic reaction. Structural changes were observed with steam explosion with 11.28% reduction of the crystallinity index attained with the lowest chitin/water ratio (0.1g/mL). Pretreated chitins reached the highest production of reducing sugars (0.37 mg/mL) and GlcNAc (0.59 mg/mL) in 23.6% yield.

Effect of temperature on chitin and astaxanthin recoveries from shrimp waste using lactic acid bacteria

The chitin and astaxanthin recoveries by lactic acid fermentation of shrimp wastes (Litopenaeus sp) were conducted in bed-column reactors at 15, 20, 25, 30, 35, 40 and 45 degrees C. The response surface methodology showed that the fermentations carried out in the 27-36 degrees C temperature range with lactic acid above 0.319 mmol/g resulted in the highest demineralization. The maximal deproteinizations were attained from 30 to 40 degrees C. The extraction of free-astaxanthin did not present significant differences between 20 and 35 degrees C and the proportion of cis-stereoisomer forms increased with temperature. The growth rates of Lactobacillus plantarum were estimated in the 15-45 degrees C range and analyzed by Arrhenius and square root models. The cardinal values were 3.94 and 51.7 degrees C for minimum and maximum temperatures, respectively, with activation energy of 43.38 Jmol(-1).

One-solvent extraction of astaxanthin from lactic acid fermented shrimp wastes

Free astaxanthin one-solvent extractions with ethanol, acetone, and liquid 1,1,1,2-tetrafluoroethane from raw and lactic acid fermented (ensilaged) shrimp residues were investigated. The total carotenoid recovery from ensilaged shrimp wastes was higher than that from non-ensilaged ones as assessed by HPLC analyses. Acetone gave the highest extraction yields of free astaxanthin with up to 115 microg/g of material. Moreover, liquid tetrafluoroethane is reported for the first time in a successful one-solvent extraction of carotenoids from shrimp.

Influence of water activity in the synthesis of galactooligosaccharides produced by a hyperthermophilic β-glycosidase in an organic medium

The present study evaluated the influence of water activity and lactose concentration on the synthesis of galactooligosaccharides (GOS), by means of a hyperthermophilic beta-glycosidase in an organic system. The production of GOS gradually grew as water activity increased in the reaction system; later, their synthesis decreased as water activity increased. The authors used the response surface methodology to study how different water activities and different concentrations of lactose influenced the synthesis of GOS and their length. In every case, the variable that proved to have the greatest effect on GOS synthesis was water activity. Maximum GOS3 synthesis was reached at a water activity interval of 0.44-0.57, with lactose concentrations of 0.06%-0.1%, while GOS4 and GOS5 maxima were reached at water activity intervals of 0.47-0.57 and 0.49-0.60, respectively. The research showed that higher water activity was required to synthesize GOS of greater length. Synthesis of GOS would then depend on the flexibility of the enzyme, which in turn would depend on water activity of the reaction system. This hypothesis was supported by experiments in which the reaction temperature was modified in order to change the flexibility of the enzyme, thus leading to longer GOS.

The lipase-catalyzed hydrolysis of lutein diesters in non-aqueous media is favored at extremely low water activities

The enzymatic hydrolysis of a mixture of lutein diesters from Marigold flower (Tagetes erecta) was performed both in organic solvents and supercritical CO(2) (SC-CO(2)) using two commercial lipases: lipase B from Candida antarctica (Novozym 435) and the lipase from Mucor miehei (Lipozyme RM IM). Both lipases showed an unexpected dependence of initial reaction rate with the initial water activity (a(wi)) in hexane, with the highest rates of hydrolysis taking place at the lowest a(wi) of the biocatalyst particles. The same result was observed using isooctane, toluene, or SC-CO(2). It is proposed that an increase in a(wi) generates a hydrophilic microenvironment that prevents efficient partitioning of the highly hydrophobic lutein diesters to the enzyme. The critical role of water in this system has not been reported for other hydrolytic reactions in low water media. Calculations of water available for hydrolysis from isotherm analysis, Karl-Fischer titration, and substrate conversion at a(wi) = 0.13, indicate that the extent of reaction is not limited by the amount of available water. Accordingly, the enzyme that holds the largest amount of water after prehydration at the same a(wi) (0.13) will yield the greatest substrate conversion and concentration of the free lutein product. The highest conversion occurred in SC-CO(2), which opens up new opportunities to develop a combined extraction-reaction process for the environmentally benign synthesis of lutein, an important nutraceutical compound.

Solubility of purified lutein diesters obtained from Tagetes erecta in supercritical CO(2) and the effect of solvent modifiers

Purified lutein diesters deposited on commercial nonporous glass beads were solubilized in supercritical CO(2) in a computerized batch extractor, and their solubilities were compared to their solubilities in hexane. Densities of 0.7, 0.8, and 0.9 g/mL were evaluated without modifiers. Both pressure and temperature increased solubility, although temperatures >50 degrees C promoted carotenoid loss as determined by mass balance. Solubility was enhanced by the use of modifiers and was related to their log P. Chloroform (log P = 2) increased 2.8 times the amount of solubilized lutein diesters compared to pure CO(2) at the same extraction conditions (0.9 g/mL and 40 degrees C) to yield 65% of the amount extracted with hexane. Supercritical CO(2) extraction of lutein diesters could represent a cleaner technology as compared to the current industrial use of hexane with important ecological and health-related implications.

Purification and characterization of an inulinase produced by a Kluyveromyces marxianus strain isolated from blue agave bagasse

Exo-inulinases are versatile enzymes that have gained attention in recent years due to their ability to hydrolyze linear and branched polyfructose chains found in inulines. Agavin, a branched inulin, is found in Agave plant, the raw matter to produce tequila. Our group has isolated several microbial strains from agave bagasse, an agro-industrial residue from tequila production that increases yearly. Strain ISO3, identified as Kluyveromyces marxianus, showed a remarkable activity towards agavin, and from its fermentation liquor an inulinolytic enzyme (Inu-ISO3) was purified. The isolated enzyme is a glycosylated dimeric protein with a molecular mass of ~256 kDa, as determined by DLS and SEC. The enzyme has an isoelectric pH of 4.6 and has both inulinase and invertase activities with an I/S ratio (ratio of activity with agavin to activity with sucrose) of 1.39. The enzyme has temperature and pH optima of 50 °C and 5.5, respectively, and follows hyperbolic kinetics with agavin (k_cat of 339 ± 27 s^-1 and K_M of 11.8 ± 1.5 mM). The remarkable activity of Inu-ISO3 on linear and branched inulin spotlights this enzyme as a potential player in the treatment of agricultural residua for the generation of added-value products.