Sustainable livestock production? Industrial agriculture versus pastoralism

Feeding our growing world population and preserving our natural resource base is a major agricultural challenge set to get harder. Despite agricultural productivity gains in many areas, roughly a billion people continue to suffer from chronic hunger.1 Meanwhile, we will likely add about 2.5 billion people to the planet by 2050.2 Yet providing enough nutrition for current and future generations is entirely possible, if we make the best use of Earth’s finite natural resources, especially arable land. Notably, one agricultural sector – livestock – places excessive demands on our resource base. But this is mainly due to globalized, industrial meat production methods. Tragically, the most sustainable livestock producers – herders and other mobile, smaller-scale livestock keepers – have been marginalized by mainstream agricultural policy for decades. It is high time for a course correction.

Cultivation strategies to enhance productivity of Pichia pastoris: A review.

Pichia pastoris, a methylotrophic yeast, is an established system for the production of heterologous proteins, particularly biopharmaceuticals and industrial enzymes. To maximise and optimise the production of recombinant products, recent molecular research has focused on numerous issues including the design of expression vectors, optimisation of gene copy number, co-expression of secretory proteins such as chaperones, engineering of glycosylation and secretory pathways, etc. However, the physiological effects of different cultivation strategies are often difficult to separate from the molecular effects of the gene construct (e.g., cellular stress through over-expression or incorrect post-translational processing). Hence, overall system optimisation is difficult, even though it is urgently required in order to describe and understand the behaviour of new molecular constructs. This review focuses on particular aspects of recombinant protein production related to variations in biomass growth and their implications for strain design and screening, as well as on the concept of rational comparisons between cultivation systems for the development of specific production processes in bioreactors. The relationship between specific formation rates of secreted recombinant proteins, qp, and specific growth rates, μ, has been analysed in a conceptual attempt to compare different systems, particularly those based on AOX1/methanol and GAP/glucose, and this has now evolved into a pivotal concept for bioprocess engineering of P. pastoris.