Mette Dines Cantor

Production of Bread, Cheese and Meat

Historic references to fermentation of dough for baking and fermentation of beer originate from the Sumerians and the Babylonians and, under the Pharaohs in ancient Egypt, the brewing of beer was a trade (Jorgensen 1948). At that time, the fermentation of bread was achieved by using a mixture of yeast and lactic acid bacteria maintained in a dough medium. After each fermentation, a portion of the dough was retained for starting the next batch or a close connection with beer brewing was established so that surplus yeast from breweries was used for production of bread. These same methods are still used in certain regions in Africa and probably other parts of the world where ancient technologies have survived and can be experienced today. In the industrialised part of the world, these methods remained in use, and did not change until late in the eighteenth century when yeast was first propagated for direct use in bread making in the Netherlands by the so-called Dutch method, which had a very low efficiency. As a result of the work of Louis Pasteur and the Danish botanists, Emil Christian Hansen and Alfred Jorgensen and others in the late nineteenth century, the role of oxygen in yeast propagation was realised, the anaerobic condition of fermentation (“life without oxygen”) was understood, Saccharomyces cerevisiae was described and the use of pure cultures was introduced. This was a very significant breakthrough for the industrialised production of baker’s yeast. A similar process improvement followed in 1920, with the introduction of the “fed-batch” process. In this process, sugar is fed incrementally during yeast propagation, avoiding repressions and leading to increased biomass production. It forms the basis of commercial processes used today for manufacturing baker’s yeast, and has developed into a highly centralised industry offering a cheap bulk commodity This is contrary to the historical development of other industrial yeast cultures like brewer’s yeast (Jorgensen 1948). For reviews on the history of baker’s yeast, see Rose and Vijayalakshmi (1993) and Jenson (1998).

Evaluation of in situ valine production by Bacillus subtilis in young pigs.

Mutants of Bacillus subtilis can be developed to overproduce Val in vitro. It was hypothesized that addition of Bacillus subtilis mutants to pig diets can be a strategy to supply the animal with Val. The objective was to investigate the effect of Bacillus subtilis mutants on growth performance and blood amino acid (AA) concentrations when fed to piglets. Experiment 1 included 18 pigs (15.0±1.1 kg) fed one of three diets containing either 0.63 or 0.69 standardized ileal digestible (SID) Val : Lys, or 0.63 SID Val : Lys supplemented with a Bacillus subtilis mutant (mutant 1). Blood samples were obtained 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding and analyzed for AAs. In Experiment 2, 80 piglets (9.1±1.1 kg) were fed one of four diets containing 0.63 or 0.67 SID Val : Lys, or 0.63 SID Val : Lys supplemented with another Bacillus subtilis mutant (mutant 2) or its parent wild type. Average daily feed intake, daily weight gain and feed conversion ratio were measured on days 7, 14 and 21. On day 17, blood samples were taken and analyzed for AAs. On days 24 to 26, six pigs from each dietary treatment were fitted with a permanent jugular vein catheter, and blood samples were taken for AA analysis 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding. In experiment 1, Bacillus subtilis mutant 1 tended (P<0.10) to increase the plasma levels of Val at 2 and 3 h post-feeding, but this was not confirmed in Experiment 2. In Experiment 2, Bacillus subtilis mutant 2 and the wild type did not result in a growth performance different from the negative and positive controls. In conclusion, results obtained with the mutant strains of Bacillus subtilis were not better than results obtained with the wild-type strain, and for both strains, the results were not different than the negative control.

Tryptophan provision by dietary supplementation of a Bacillus subtilis mutant strain in piglets

Abstract Supplementing Bacillus (B.) subtilis mutants selected to overproduce a specific amino acid (AA) may be an alternative method to provide essential AA in pig diets. Two experiments on a B. subtilis strain selected to overproduce Trp were conducted using 8-kg pigs fed Trp-deficient diets for 20 d. B. subtilis were supplied in a low or high dose in Experiments 1 and 2, respectively. The Trp-deficient diet (0.15 SID Trp:Lys) reduced (p < .05) both gain and feed intake of piglets compared to the positive control diet (0.17 SID Trp:Lys). Supplementation of the B. subtilis strain was not able to counterbalance the Trp deficiency in any of the two experiments. No effect of B. subtilis supplementation to piglet diets was observed on the plasma AA profile. In conclusion, this mutant strain of B. subtilis was not able to compensate a Trp deficiency in the tested doses.

Chapter 37 – Blue Cheese

Blue or blue-veined cheeses are characterized by growth of the mold Penicillium roqueforti, giving them their typical appearance and flavor. Blue cheese is produced in many countries all over the world, where their own types of blue cheeses have been developed, each with different characteristics and involving different manufacturing methods. This chapter aims to review the knowledge on different aspects of blue cheese ripening, emphasizing changes in the microenvironment, for example, pH and salt gradients within the cheese matrix; the microorganisms that contribute to ripening and their interactions, that is, lactic acid bacteria, mold, and yeasts; and the various biochemical changes, that is, lipolysis, proteolysis, and aroma formation and the effect on the texture and consistency of the ripened cheese. Potential mycotoxin production is also covered. Finally, thoughts on the selection of appropriate starter and mold cultures, as well as new, possible adjunct cultures, will be discussed.

Selection of Bacillus species for targeted in situ release of prebiotic galacto-rhamnogalacturonan from potato pulp in piglets

We have previously shown that galacto-rhamnogalacturonan fibers can be enzymatically extracted from potato pulp and that these fibers have potential for exerting a prebiotic effect in piglets. The spore-forming Bacillus species are widely used as probiotics in feed supplements for pigs. In this study, we evaluated the option for further functionalizing Bacillus feed supplements by selecting strains possessing the enzymes required for extraction of the potentially prebiotic fibers. We established that it would require production and secretion of pectin lyase and/or polygalacturonase but no or limited secretion of galactanase and β-galactosidase. By screening a library of 158 Bacillus species isolated from feces and soil, we demonstrated that especially strains of Bacillus amyloliquefaciens, Bacillus subtilis, and Bacillus mojavensis have the necessary enzyme profile and thus the capability to degrade polygalacturonan. Using an in vitro porcine gastrointestinal model system, we revealed that specifically strains of B. mojavensis were able to efficiently release galacto-rhamnogalacturonan from potato pulp under simulated gastrointestinal conditions. The work thus demonstrated the feasibility of producing prebiotic fibers via a feed containing Bacillus spores and potato pulp and identified candidates for future in vivo evaluation in piglets.