Preventing phage lysis of Lactococcus lactis in cheese production using a neutralizing heavy-chain antibody fragment from llama.

Bacteriophage infection is still a persistent problem in large dairy processes despite extensive studies over the last decades. Consequently, new methods are constantly sought to prevent phage infection. In this paper, we show that phage neutralizing heavy-chain antibody fragments, obtained from Camelidae and produced at a large scale in the generally regarded as safe microorganism Saccharomyces cerevisiae, can effectively be used to impede phage induced lysis during a cheese process. The growth inhibition of the cheese starter culture by 10(5) pfu/ml cheese-milk of the small isometric-headed 936-type phage p2 was prevented by the addition of only 0.1 microg/ml (7 nM) of the neutralizing antibody fragment. The use of such antibody fragments in cheese manufacturing are a realistic and interesting option because of the small amount of antibody fragments that are needed. Moreover the antibodies are produced in a food grade microorganism and can easily be isolated from the fermentation liquid in a pure and DNA free form.

The role of fungal polysaccharidases in the hydrolysis of cell wall materials from sunflower and palm-kernel meals.

Main fractions from multi-component polysaccharidase preparations (Driselase, Gamanase and an experimental preparation of fungal origin), previously used for the enzymic treatment of cell wall materials from sunflower and palm-kernel meals, were sub-fractionated by different chromatographic techniques to evaluate the contribution of each of their constituent activities in cell wall degradation. Based on activity measurements, 5- to 10-fold purification was achieved for the major enzymes but residual side-activities were still detectable in most sub-fractions. Solubilization of non-starch polysaccharides from the cell wall materials by the resulting pectolytic, xylanolytic, cellulolytic and mannanolytic sub-fractions and by highly purified glucanases, arabinanases and xylanases was, when acting individually, very low (1% to 5%). With few exceptions, the solubilizing effect of the main fractions could only be slightly enhanced by supplementation with pectolytic, cellulolytic or mannanolytic sub-fractions or by highly purified enzymes. The extent of solubilization remained mostly lower than the sum of both individually obtained values. In the degradation of palm-kernel cell wall material, however, synergistic action of mannanases and glucanases was observed. The hydrolysis of pectic compounds in sunflower cell wall material was most effective when polygalacturonases, arabinanases and rhamnogalacturonan-degrading activities were applied together. The resistance of 4-O-methyl-glucuronoxylan, the major hemicellulosic polymer in the cell wall material from sunflower meal, to enzymic hydrolysis was not only caused by its location in the cell wall or interlinkage to other polymers but also by its primary structure. Neither purified endo-xylanase nor the crude parent preparation were able to achieve complete hydrolysis of this polysaccharide after extraction.