Enzymatic production of lactulose by fed-batch and repeated fed-batch reactor.

The effects of the most significant operational variables on reactor performance of fed-batch and repeated fed-batch were evaluated in the lactulose production by enzymatic transgalactosylation. Feed flowrate in the fed stage (F) and fructose to lactose molar ratio (Fr/L) were the variables that mostly affected the values ​​of lactulose yield (YLu), lactulose productivity (πLu) and selectivity of transgalactosylation (SLu/TOS). Maximum YLu of 0.21 g lactulose per g lactose was obtained at 50% w/w inlet carbohydrates concentration (IC) of, 50 °C, Fr/L 8, F 1 mL⋅min-1, 200 IU∙gLactose-1 reactor enzyme load and pH 4.5. At these conditions the selectivity was 7.4, productivity was 0.71 gLu∙g-1∙h-1and lactose conversion was 0.66. The operation by repeated fed batch increases the efficiency of use of the biocatalysts (EB) and the accumulated productivity compared to batch and fed batch operation with the same biocatalyst. EB obtained was 4.13 gLu∙mgbiocatalyst protein-1, 10.6 times higher than in fed-batch.

Oligosacáridos y polisacáridos no digeribles: una fuente de salud para los adultos mayores / Non-digestible oligosaccharides and polysaccharides: a source of health for older people

RESUMEN Los adultos mayores son especialmente vulnerables a sufrir enfermedades asociadas al tracto gastrointestinal, ya que el envejecimiento conlleva naturalmente a un desbalance en la diversidad y cantidad de los microorganismos presentes en el intestino. Por ello, la suplementación de su dieta con oligosacáridos y polisacáridos no digestibles (OPND) ha cobrado gran relevancia científica. Esto, con el propósito de prevenir y revertir, en parte, los cambios negativos en la microbiota intestinal derivados del envejecimiento. Se ha observado que la suplementación de OPND en adultos mayores genera variados beneficios, entre los que destacan una mejora en el sistema inmune, una mayor absorción de calcio, reducción en la incidencia de alergias, reducción de la constipación y una disminución en los niveles de glicemia y colesterol sanguíneos. Debido a que, los efectos del consumo de OPND en adultos mayores han sido escasamente discutidos en la literatura científica en idioma castellano, el propósito de esta revisión es abordar el tema haciendo énfasis en la realidad chilena y latinoamericana. Ello, con miras a fomentar la incorporación de OPND en alimentos y programas de alimentación dirigidos específicamente a personas de la tercera edad.

ABSTRACT Since aging naturally leads to an imbalance in the diversity and quantity of microorganisms present in the intestine, older people are particularly vulnerable to diseases associated with the gastrointestinal tract. Thus, supplementing the diet of elderly persons with non-digestible oligosaccharides and polysaccharides (OPND) has gained scientific relevance. Supplementation aims to prevent and (partially) revert the negative changes in intestinal microbiota due to aging. It has been observed that OPND supplementation in older adults provides several benefits, including an improvement in the immune system, increased calcium absorption, a reduction in the incidence of allergies, a reduction in constipation and a decrease in blood levels of cholesterol and glucose. Because the effects of OPND supplementation in older adults has been scarcely discussed in the scientific literature in the Spanish language, the purpose of this review is to address the issue with emphasis on the Chilean and Latin-American reality. The article promotes the incorporation of OPND in processed food and feeding programs specifically designed for older people in Latin America.

Synthesis of Lactulose in Continuous Stirred Tank Reactor With ß-Galactosidase of Apergillus oryzae Immobilized in Monofunctional Glyoxyl Agarose Support.

Lactulose synthesis from fructose and lactose in continuous stirred tank (CSTR) reactor operation with glyoxyl-agarose immobilized Aspergillus oryzae ß-galactosidase is reported for the first time. The effect of operational variables: inlet concentrations of sugar substrates, temperature, feed substrate molar ratio, enzyme loading and feed flow rate was studied on reactor performance. Even though the variation of each one affected to a certain extent lactulose yield (Y Lactulose ), specific productivity (π Lactulose ) and selectivity of the reaction (lactulose/transgalactosylated oligosaccharides molar ratio) (S Lu/TOS ), the most significant effects were obtained by varying the inlet concentrations of sugar substrates and the feed substrate molar ratio. Maximum Y Lactulose of 0.54 g⋅g-1 was obtained at 50°C, pH 4.5, 50% w/w inlet concentrations of sugar substrates, feed flowrate of 12 mL⋅min-1, fructose/lactose molar ratio of 8 and reactor enzyme load of 29.06 IU H ⋅mL-1. At such conditions S Lu/TOS was 3.7, lactose conversion (X Lactose ) was 0.39 and total transgalactosylation yield was 0.762 g⋅g-1, meaning that 76% of the reacted lactose corresponded to transgalactosylation and 24% to hydrolysis, which is a definite advantage of this mode of operation. Even though X Lactose in CSTR was lower than in other reported modes of operation for lactulose synthesis, transgalactosylation was more favored over hydrolysis which reduced the inhibitory effect of galactose on ß-galactosidase.

Continuous enzymatic synthesis of lactulose in packed-bed reactor with immobilized Aspergillus oryzae ß-galactosidase.

Lactulose synthesis from fructose and lactose in continuous packed-bed reactor operation with glyoxyl-agarose immobilized Aspergillus oryzae ß-galactosidase is reported for the first time. Alternative strategies to conventional batch synthesis have been scarcely explored for lactulose synthesis. The effect of flow rate, substrates ratio and biocatalyst-inert packing material mass ratio (MB/MIM) were studied on reactor performance. Increase in any of these variables produced an increase in lactulose yield (YLu) being higher than obtained in batch synthesis at comparable conditions. Maximum YLu of 0.6 g·g-1 was obtained at 50 °C, pH 4.5, 50% w/w total sugars, 15 mL·min-1, fructose/lactose molar ratio of 12 and MB/MIM of 1/8 g·g-1; at such conditions yield of transgalactosylated oligosaccharides (YTOS) was 0.16 g·g-1, selectivity (lactulose/TOS molar ratio) was 5.4 and lactose conversion (XLactose) was 28%. Reactor operation with recycle had no significant effect on yield, producing only some decrease in productivity.