Bayram & Özçelik

P19: Production of food grade carotenoids from microorganisms

P20: Degradation of tannic acid by cell-free extracts of Lactobacillus plantarum

H. Rodríguez, B. de las Rivas¹, C. Gómez-Cordovés & R. Muñoz Instituto de Fermentaciones Industriales, CSIC, Madrid, SPAIN

In foods, tannins are considered nutritionally undesirable. However, the intake of a small quantity of the right kind of tannins may be beneficial to human health. It has been found that the higher the molar mass of tannin molecules, the stronger the antinutritional effects and the lower the biological activities.

Microbial degradation is one of the efficient ways to degrade large molecular tannins into smaller molecular tannins with valuable bioactivities. In this work we evaluated the ability of Lactobacillus plantarum to degrade hydrolysable tannins. Significative reduction of tannic acid was not observed during incubation in the presence of L. plantarum cells after 7 days incubation. However, tannic acid was effectively degraded by cell-free extracts containing soluble proteins from L. plantarum. By HPLC analysis, almost a complete tannic acid degradation was observed in the three commercial tannic acid samples assayed. By using HPLC-DAD/ESI-MS, we partially determined the composition of tannic acid from Quercus infectoria galls. This tannic acid is a gallotannin mainly composed of monomers to tetramers of gallic acid. We studied the mechanism of its degradation by L. plantarum. The results indicated that L. plantarum degrades gallotannins by depolymerization of high molecular weight tannins and a reduction of low molecular weight tannins. Gallic acid and pyrogallol were detected as final metabolic intermediates

P21: Bioconversion of lignocellulosic biomass to xylooligosaccharides

O. Akpinar, K. Erdogan & S. Bostanci

Gaziosmanpasa University, Department of Food Engineering, Tasliciftlik, Tokat, Turkey

Key words: Xylooligosaccharides, tobacco stalks, cotton stalks, sunflower stalks, wheat straw

Different agricultural wastes, namely tobacco stalk (TS), cotton stalk (CS), sunflower stalk (SS) and wheat straw (WS) were tested for the production of xylooligosaccharide (XO). XO production was performed by enzymatic hydrolysis of xylans which were obtained by alkali extraction from the agricultural wastes. These four agricultural wastes contained different amount of xylan, cellulose and lignin and the xylan obtained from these source contained different amount of sugar and uronic acid.

Xylan from WS had arabino glucoronoxylan structure the while the other xylans had glucoronoxylan structure. Different xylanase preparations were evaluated for production XO from these xylan sources.

A. niger xylanase produced lower amount of XO from wheat straw xylan (WSX) than cotton stalk xylan (CSX), sun flower xylan (SSX) and tobacco stalk xylan (TSX) while T. longibrachiatum xylanase hydrolyzed highly branced WSX better. A.niger xylanase produced less amount of xylose than T. longibrachiatum xylanase, and the hyrolysis product of A.niger xylanase contained different amount of oligosaccharides. Regardless of the structural differences of the xylan types presented in this paper, all xylans generated XO with different degree of polymerization (DP), but the DP of XO depended on the enzyme specifity and the structure of substrate.

P22: Assembly and stability of polyelectrolyte multilayers and their potential for the controlled delivery applications

M. Sujka*, T. R. Noel, R. Parker & P. J. Wilde

Institute of Food Research, Norwich Research Park, Colney, Norwich, UK e-mail: Marta.Sujka@bbsrc.ac.uk

The requirement to encapsulate an active ingredient/therapeutic under one set of environmental conditions, and obtain release under another set of conditions, is well established in the pharmaceutical sector. In terms of food delivery, this approach could have the potential to deliver improvements in food quality through the controlled release of aroma, flavour and nutrients. One way of achieving this goal is through the use of environmentally responsive matrices or coatings. In this study we investigated the assembly and responsiveness of polygalacturonic acid (PGA)-based multilayers to variations in salt concentration and pH. Layer-by-layer assembly of 10-layer multilayers at pH 7.0 was monitored with FTIR-ATR and QCMD. The results showed non-linear type growth for the poly-L- lysine (PLL)/PGA and chitosan/PGA structures, while the lysozyme/PGA structure showed limited growth. In the latter case deposition and washing steps led to stripping and desorption. The limited growth of the lysozyme/PGA systems was attributed to the globular structure of lysozyme. Dual polarisation interferometry indicated the multilayers varied in density, ranging from 0.25 mg solids/mL (chitosan) to 0.50 mg solids/mL (PLL). Salt responsiveness (increasing NaCl concentrations from 30 mM to 200 mM and back to 30 mM) only affected composition for the lysozyme/PGA assembly, where the increase of ionic strength resulted in a selective loss of lysozyme (~60%). Multilayers showed partial solubilisation in response to pH changes from 7.0 to 1.6 and back to 7.0. FTIR-ATR showed directly the changing charge as the carboxylate groups of PGA became protonated at low pH and ionised as the pH is increased. In all cases preferential solubilisation of polycation compared to polyanion occurred with ~ 50%, 58% and 65% loss of PLL, chitosan, lysozyme, respectively. The partial solubilisation of the PGA-based multilayers contrasted with the full solubilisation previously observed for PLL/pectin multilayers¹. The results showed that a range of different structures can be assembled and pH responsive behaviour obtained.

Acknowledgements

The authors thank the BBSRC for financial support through its core strategic grant and grants BB/E011004/1 and BB/E013171/1.