Abstract: Aerobic heterotrophic bacteria (AHB) and purple non-sulfur bacteria (PNSB) are typically explored as two separate types of microbial protein, yet their properties as respectively a bulk and added-value feed ingredient make them appealing for combined use. The feasibility of cocultivation in a sequential photo- and chemotrophic approach was investigated. First, mapping the chemotrophic growth kinetics for four Rhodobacter, Rhodopseudomonas and Rhodospirillum species on different carbon sources showed a preference for fructose (µmax 2.4–3.9 d−1 28 °C; protein 36–59%DW). Secondly, a continuous photobioreactor inoculated with Rhodobacter capsulatus (VFA as C-source) delivered the starter culture for an aerobic batch reactor (fructose as C-source). This two-stage system showed an improved nutritional quality compared to AHB production: higher protein content (45–71%DW), more attractive amino/fatty acid profile and contained up to 10% PNSB. The findings strengthen protein production with cocultures and might enable the implementation of the technology for resource recovery on streams such as wastewater.

Abstract: This chapter lays out a conservation timeline, from past to future, for the Amsterdam version of Van Gogh's Sunflowers. It starts by considering the restoration history of the painting in order to assess its current physical state, and looks ahead to formulate an appropriate strategy for future conservation treatment and display. Due attention is paid to the two recorded episodes of restoration performed in 1927 and 1961 by the Dutch restorer, Jan Cornelis Traas. Based on physical and chemical investigation of Sunflowers we attempt to reconstruct what these former treatments (which are barely documented) entailed and consider the repercussions for the present condition of the painting. The former interventions by Traas also serve as a benchmark to reflect on current choices made, highlighting the extent to which ideas and methodologies have continued to evolve over the past century as conservation has moved further away from being a singularly craft-based activity to become an established historical and scientific discipline underpinned by ethical guidelines. Jan Cornelis Traas (1898–1984) As mentioned, the two main recorded interventions to the Amsterdam Sunflowers may be associated with the Dutch restorer, Jan Cornelis Traas, who treated the picture in 1927, close to the start of his career, and again in 1961, shortly before he retired. Traas was the first restorer to be appointed at the Mauritshuis in The Hague where he worked from 1931 to 1962 and treated hundreds of paintings, including iconic masterpieces such as Girl with a Pearl Earring by Johannes Vermeer. Yet despite the magnitude and importance of his restoration oeuvre, J.C. Traas (as he is usually referred to in surviving documents), has remained somewhat obscure. He is shown here in the only known surviving photograph of him at work, shortly before he retired (fig. 7.1). Unlike his illustrious contemporaries, A. Martin de Wild (1899–1969) and Helmut Ruhemann (1891–1973), for example, Traas did not publish anything, he appears to have kept no records of his work and no personal archive is known. However, the study of some newly discovered historical documents, combined with physical examination of Sunflowers and a large number of other works he treated, allows us to recover an idea of his working practices and approaches viewed within the context of his day.