Tubular cellulose/starch gel composite as food enzyme storehouse
Introduction
Composites are materials that comprise of two or more distinct components with significantly different physicochemical properties and/or new functionalities (Miao & Hamad, 2013). Recently composite materials derived from bio-based sources have attracted great attention due to growing concerns for sustainability and environmental protection. Specifically, efforts have been made to produce composite materials based on biodegradable polymers such as poly(lactic acid) (Brzezinski and Biela, 2014, Kumar et al., 2014), poly(hydroxyalkanoates) (Loureiro, Esteves, Viana, & Ghosh, 2014), starch (Gilfillan et al., 2014, Servetas et al., 2013), and cellulose (Miao & Hamad, 2013). Cellulosic materials have several advantages; they are biodegradable, CO2 neutral, abundant, versatile, and cheap. Cellulose, a β-d-glucose biopolymer, is the main component of all plant cell walls. It is the most abundant renewable polymer source, considered an almost inexhaustible raw material for eco-friendly biocompatible products (Klemm, Heublein, Fink, & Bohn, 2005). Wood cellulose forms a rigid composite with hemicelluloses and lignin, cross-linked with smaller amounts of pectic polysaccharides and proteins, with varying proportions between species (Balat and Demirbas, 2009, Klemm et al., 2005). Removal of lignin from wood cellulose with alkaline treatment leads to a porous, tubular cellulosic material (TC), containing nano- and micro-scale pores (Koutinas et al., 2012).
Starch is also a natural polymer, second most abundant type of biomass after cellulose (Le Corre, Bras, & Dufresne, 2010). It is used in a wide variety of food and industrial applications in native form or after chemical/physical modification. Recently, due to its renewable and biodegradable character and relatively low cost, starch is gaining attention as a filler in nanocomposites to replace fossil-based ones such as carbon black (Le Corre et al., 2010). Another interesting application of starch, as well as cellulose and other biopolymers, is the development of composites for co-immobilization of different microorganisms in order to simultaneously conduct different bioprocesses into the same bioreactor, thus leading to reduction of production and investment costs. For example, a composite of TC with starch gel (SG) was produced for simultaneous alcoholic (Saccharomyces cerevisiae entrapped in SG) and malolactic (Oenococcus oeni entrapped in TC) fermentation of wine (Servetas et al., 2013). The deposition of SG into the TC tubes reduces the dimensions of the TC tubes, which in combination with the removal of the lignin portion from TC, creates a material with micro- and nano-scale porosity (Koutinas et al., 2012, Servetas et al., 2013). Following the above works, the two-layer TC/SG composite biocatalyst was considered interesting for the immobilization of enzymes. Enzyme immobilization has been defined as the attachment or incorporation of enzymes onto or into large structures, via simple adsorption, covalent attachment, or encapsulation (Kim, Grate, & Wang, 2006). Various materials have been developed for the immobilization of enzymes. Natural, organic, and large surface biopolymers are more attractive due to the fact that they are safe and cheap for food bioprocessing (Koutinas et al., 2012). Therefore, the aim of the present work was to study the surface characteristics of the TC/SG composite and evaluate its suitability for food enzyme (rennin) immobilization and storage.
Section snippets
Materials and preparation of the TC/SG composite
Corn starch and rennin from Mucor miehei were obtained from Sigma Aldrich. Wood sawdust was obtained from a local lumber mill. Wood sawdust was treated with 1% NaOH solution at 80 °C for 3 h in order to remove lignin and obtain the TC material (Koutinas et al., 2012). TC was washed with deionised water several times in order to remove the remaining alkaline solution and also the solubilized lignin. For the preparation of SG, 4 g of starch were mixed thoroughly with 50 mL of deionised water under
Results and discussion
The TC material is produced after lignin removal from lignocellulosic biomass. Lignin is dispersed in small fibrils and its removal creates micro and nano-tubes in the material (Koutinas et al., 2012). The aim of this study was to use this material for enzyme storage by entrapment of in the tubes of TC and use as a biocatalyst for repeated bioprocessing (e.g. milk coagulation). Cells immobilized in TC have been successfully used for various alcoholic and lactic acid fermentation processes (
Conclusions
The TC/SG composite had reduced pore volume and pore size compared to plain TC. Comparing composites with different percentages of SG, the specific surface area seemed to decrease with increased SG ratio. The XRD results also showed a decrease of crystallinity with increased SG ratio in the composite. The composite was used as an insoluble carrier for entrapment of the dairy enzyme rennin, leading to the production of an active biocatalyst for milk coagulation. Porous materials such as the
Acknowledgements
This research has been co-financed by the European Union (European Regional Development Fund – ERDF) and Greek national funds through the Operational Program “Competitiveness and Entrepreneurship” of the National Strategic Reference Framework (NSRF) 2007–2013 – National Action “Cooperation 2011: Partnerships of Production and Research Institutions in Focused Research and Technology Sectors” of General Secretariat for Research and Technology (Contract Nr. 11SYN_2_1374).
References (21)
- et al.
Polylactide nanocomposites with functionalized carbon nanotubes and their stereocomplexes: A focused review
Materials Letters
(2014) - et al.
The effects of various pulping conditions on crystalline structure of cellulose in cotton linters
Polymer Degradation and Stability
(2003) - et al.
Biofibres and biocomposites
Carbohydrate Polymers
(2008) - et al.
Nanostructures for enzyme stabilization
Chemical Engineering Science
(2006) - et al.
Immobilization technologies and support materials suitable in alcohol beverages production: A review
Food Microbiology
(2004) - et al.
Lactic acid fermentation by cells immobilised on various porous cellulosic materials and their alginate/poly-lactic acid composites
Bioresource Technology
(2014) - et al.
Development of polyhydroxyalkanoates/poly(lactic acid) composites reinforced with cellulosic fibers
Composites Part B
(2014) - et al.
Saccharomyces cerevisiae and Oenococcus oeni immobilized in different layers of a cellulose/starch gel composite for simultaneous alcoholic and malolactic wine fermentations
Process Biochemistry
(2013) - et al.
Sorption and pore condensation behavior of pure fluids in mesoporous MCM-48 silica, MCM-41 silica, SBA-15 silica and controlled-pore glass at temperatures above and below the bulk triple point
Applied Surface Science
(2002) - et al.
Bio-oil from pyrolysis of black alder wood
Energy Sources A
(2009)
Cited by (19)
Ethanol from cellulose and cellobiose of woody-substrates in a single stage of 3-combined-bioprocesses employing a non-GM yeast cell-factory
2023, Biocatalysis and Agricultural BiotechnologyCarbohydrate nanotubes production and its techno-economic validation
2023, Bioresource Technology ReportsResearch progress on polysaccharide/protein hydrogels: Preparation method, functional property and application as delivery systems for bioactive ingredients
2021, Food Research InternationalCitation Excerpt :Simulated gastrointestinal digestion experiments indicated that the composite hydrogels could enable curcumin to be stable in stomach and be released in small intestine. Barouni, Petsi, Kanellaki, Bekatorou, and Koutinas (2015) prepared t the cellulose-starch gels as a food enzyme storehouse. This composite hydrogel could entrap the insoluble dairy enzyme rennin to produce an active biocatalyst for milk coagulation, which has a prospective utilization in the research of food enzyme.
Enzyme immobilization strategies and bioprocessing applications
2020, Biomass, Biofuels, Biochemicals: Advances in Enzyme Catalysis and TechnologiesA ready-to-use freeze-dried juice and immobilized yeast mixture for low temperature sour cherry (Prunus cerasus) wine making
2019, Food and Bioproducts ProcessingCitation Excerpt :In this work, a ready-to-use mixture of freeze-dried materials (immobilised yeast and sour cherry juice) was used for sweet fruit wine production by low-temperature fermentation. Yeast was immobilized on a porous cellulosic material (DC), obtained after wood sawdust delignification, that has been successfully used as cell immobilization carrier to promote many types of bioprocesses in food and beverage production, including extremely low temperature fermentations (Koutinas et al., 2012; Barouni et al., 2015; Ganatsios et al., 2014). As it can be observed in Fig. 1, DC exhibits a tubular network that facilitates cell entrapment.