PVA-Hydrogel Entrapped Candida Guilliermondii for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Abstract

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing-thawing method. Entrapment experiments were planned according to a 2(3) full factorial design, using the PVA concentration (80, 100, and 120 g L(-1)), the freezing temperature (-10, -15, and -20 degrees C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 degrees C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L(-1), a xylitol yield on consumed xylose of 0.49 g g(-1) and a xylitol volumetric productivity of 0.24 g L(-1) h(-1) were obtained.

Potential of hydrothermal treatments in lignocellulose biorefineries

“…Xylitol, a five‐carbon sugar alcohol employed as a non‐cariogenic, low‐calorie sweetener suitable for diabetic patients, can be produced by fermentation of xylose‐containing hydrolyzates with yeasts such as Debaryomyces hansenii , Pachysolen tannophilus, Candida guilliermondii, Candida parapsilosis or Candida tropicalis . A comparative evaluation of different micro‐organisms31 and operational methods based on the utilization of immobilized cells32,33 are fresh inputs in the field. Cellulolytic enzymes. Cellulases can be produced by culturing fungi in media containing HS, an operational strategy that may play a role in the development of integrated biorefineries.…”

Incorporação de fonte de nitrogênio em partículas de PVA e alginato de sódio e estudo da influência de ciclos de congelamento/descongelamento na caracterização do produto

“…A solução de PVA+AS foi aquecida a aproximadamente 80 °C e gotejada através de uma bomba peristáltica da Tecnal, modelo TE-BP-01-MINI, a 9,5 mL/min, em solução de CaCl 2 a 5% [1] estando esta, em banho de gelo e sob agitação magnética [8] . As partículas formadas foram mantidas na solução de CaCl 2 por 3 horas [18] .…”

Biomaterials/Cryogels

“…The chemical structure of PVA provides stabilization of cells and proteins during freezing in solution, the effect being similar to that of low-molecular-weight polyols including sugars. Entrapment of bacterial cells into PVA cryogels was studied as a technique to design bioreactors for conversion of xylose to xylitol (da Kunha et al, 2009) and for denitrification of water (Zhang et al, 2009). The composites with immobilized cells could be used as biocatalysts or bioreactors for production of extracellular proteins or other biopolymers such as beta-cyclodextrin.…”