Toward designer milk

Genetically engineering milk

It has been thirty years since the first genetically engineered animal with altered milk composition was reported. During the intervening years, the world population has increased from 5bn to 7bn people. An increasing demand for protein in the human diet has followed this population expansion, putting huge stress on the food supply chain. Many solutions to the grand challenge of food security for all have been proposed and are currently under investigation and study. Amongst these, genetics still has an important role to play, aiming to continually enable the selection of livestock with enhanced traits. Part of the geneticist's tool box is the technology of genetic engineering. In this Invited Review, we indicate that this technology has come a long way, we focus on the genetic engineering of dairy animals and we argue that the new strategies for precision breeding demand proper evaluation as to how they could contribute to the essential increases in agricultural productivity our society must achieve.

Biofortification of milk and cheese with microelements by dietary feed bio-preparations

The present work reports studies on biofortification of milk and cheese with microelements. The diet of goats was supplemented with soya-based preparations with Cu(II), Fe(II), Zn(II) and Mn(II), produced by biosorption, instead of mineral salts. In innovative preparations, soya was the biological carrier of microelements. The utilitarian properties of the new preparations were tested in two groups (8 goats in each): experimental and control. The concentration of supplemented microelements was monitored in milk during the experiment. The collected milk was then used to produce cheese by enzymatic and acidic coagulation method. The effect of milk and cheese biofortification in microelements was confirmed. In milk, the level of the following microelements was higher than in the control: Cu(II) - 8.2 %, Mn(II) - 29.2 %, Zn(II) - 14.6 %. In cheese the content of Zn(II) obtained in enzymatic (19.8 %) and in acidic (120 %) coagulation was higher when compared to the control group. By using bio-preparations with microelements it was possible to produce new generation of functional food biofortified with microelements, by agronomic, and thus sustainable and ethically acceptable way. Biofortified milk and cheese can be used as designer milk to prevent from micronutrient deficiencies. Graphical Abstractᅟ.

Designer milk

Dairy biotechnology is fast gaining ground in the area of altering milk composition for processing and/or animal and human health by employing nutritional and genetic approaches. Modification of the primary structure of casein, alteration in the lipid profile, increased protein recovery, milk containing nutraceuticals, and replacement for infant formula offer several advantages in the area of processing. Less fat in milk, altered fatty acid profiles to include more healthy fatty acids such as CLA and ω‐fats, improved amino acid profiles, more protein, less lactose, and absence of β‐lactoglobulin (β‐LG) are some opportunities of “designing” milk for human health benefits. Transgenic technology has also produced farm animals that secrete in their milk, human lactoferrin, lysozyme, and lipase so as to simulate human milk in terms of quality and quantity of these elements that are protective to infants. Cow milk allergenicity in children could be reduced by eliminating the β‐LG gene from bovines. Animals that produce milk containing therapeutic agents such as insulin, plasma proteins, drugs, and vaccines for human health have been genetically engineered. In order to cater to animal health, transgenic animals that express in their mammary glands, various components that work against mastitis have been generated. The ultimate acceptability of the “designer” products will depend on ethical issues such as animal welfare and safety, besides better health benefits and increased profitability of products manufactured by the novel techniques.

Endless versatility in the biotechnological applications of Kluyveromyces LAC genes

Most microorganisms adapted to life in milk owe their ability to thrive in this habitat to the evolution of mechanisms for the use of the most abundant sugar present on it, lactose, as a carbon source. Because of their lactose-assimilating ability, Kluyveromyces yeasts have long been used in industrial processes involved in the elimination of this sugar. The identification of the genes conferring Kluyveromyces with a system for permeabilization and intracellular hydrolysis of lactose (LAC genes), along with the current possibilities for their transfer into alternative organisms through genetic engineering, has significantly broadened the industrial profitability of lactic yeasts. This review provides an updated overview of the general properties of Kluyveromyces LAC genes, and the multiple techniques involving their biotechnological utilization. Emphasis is also made on the potential that some of the latest technologies, such as the generation of transgenics, will have for a further benefit in the use of these and related genes.

The prospects of modifying the antimicrobial properties of milk

Milk contains a variety of substances, which inhibit the infection of pathogens. This is of benefit to the mother, safeguarding the integrity of the lactating mammary gland, but also of huge importance for protection of the suckling offspring. The antimicrobial substances in milk can be classified into two categories. First, nonspecific, broad-spectrum defense substances, which have evolved over long periods of time, and secondly, substances like antibodies, which are specifically directed against particular pathogens and have developed during the mother's lifetime. Substances in both categories may be targets for biological intervention and manipulation with the goal of improving the antimicrobial properties of milk. These alterations of milk composition have applications in human as well as in animal health.

Management strategies for agricultural biotechnology in small countries

Agricultural biotechnology is concentrated in four major countries. This paper suggests strategies for developing it in small countries, based on analysis of the world trends and the characteristics of small countries. Israel is presented as a specific case study. The main relevant trends are domination by big companies, consumer concerns on genetically modified foods, and focusing on consumer benefits and specific market niches. Small countries' disadvantages include companies that are too small to benefit fully from research, difficulty in raising funds, lack of infrastructures and experienced management personnel, and public sector research organizations that are unsuitable for commercializing research. The recommended strategies include: developing a large number of low-volume products and small market niches, forming partnerships with intermediaries (such as food companies), specializing in intermediate products (such as the seed or the gene patent), and conducting market research and cost-benefit analysis in advance. Additional strategies include developing benefits that are unique to genetically modified foods and focusing on benefits specifically for consumers who accept genetically modified foods, rather than on benefits for the average consumer. A national representative organization could buy and rent out expensive equipment, finance specific projects in return for the commercial rights, and perform collective marketing research and marketing. Israel has the advantages of a successful agricultural sector and complementary scientific research, and should focus on those fruits, vegetables, and flowers for which it already has the experience and infrastructure.

Transgenic animal bioreactors

The production of recombinant proteins is one of the major successes of biotechnology. Animal cells are required to synthesize proteins with the appropriate post-translational modifications. Transgenic animals are being used for this purpose. Milk, egg white, blood, urine, seminal plasma and silk worm cocoon from transgenic animals are candidates to be the source of recombinant proteins at an industrial scale. Although the first recombinant protein produced by transgenic animals is expected to be in the market in 2000, a certain number of technical problems remain to be solved before the various systems are optimized. Although the generation of transgenic farm animals has become recently easier mainly with the technique of animal cloning using transfected somatic cells as nuclear donor, this point remains a limitation as far as cost is concerned. Numerous experiments carried out for the last 15 years have shown that the expression of the transgene is predictable only to a limited extent. This is clearly due to the fact that the expression vectors are not constructed in an appropriate manner. This undoubtedly comes from the fact that all the signals contained in genes have not yet been identified. Gene constructions thus result sometime in poorly functional expression vectors. One possibility consists in using long genomic DNA fragments contained in YAC or BAC vectors. The other relies on the identification of the major important elements required to obtain a satisfactory transgene expression. These elements include essentially gene insulators, chromatin openers, matrix attached regions, enhancers and introns. A certain number of proteins having complex structures (formed by several subunits, being glycosylated, cleaved, carboxylated...) have been obtained at levels sufficient for an industrial exploitation. In other cases, the mammary cellular machinery seems insufficient to promote all the post-translational modifications. The addition of genes coding for enzymes involved in protein maturation has been envisaged and successfully performed in one case. Furin gene expressed specifically in the mammary gland proved to able to cleave native human protein C with good efficiency. In a certain number of cases, the recombinant proteins produced in milk have deleterious effects on the mammary gland function or in the animals themselves. This comes independently from ectopic expression of the transgenes and from the transfer of the recombinant proteins from milk to blood. One possibility to eliminate or reduce these side-effects may be to use systems inducible by an exogenous molecule such as tetracycline allowing the transgene to be expressed only during lactation and strictly in the mammary gland. The purification of recombinant proteins from milk is generally not particularly difficult. This may not be the case, however, when the endogenous proteins such as serum albumin or antibodies are abundantly present in milk. This problem may be still more crucial if proteins are produced in blood. Among the biological contaminants potentially present in the recombinant proteins prepared from transgenic animals, prions are certainly those raising the major concern. The selection of animals chosen to generate transgenics on one hand and the elimination of the potentially contaminated animals, thanks to recently defined quite sensitive tests may reduce the risk to an extremely low level. The available techniques to produce pharmaceutical proteins in milk can be used as well to optimize milk composition of farm animals, to add nutriceuticals in milk and potentially to reduce or even eliminate some mammary infectious diseases.