Improvement of 2-phenylethanol production in Saccharomyces cerevisiae by evolutionary and rational metabolic engineering

2-Phenylethanol (2-PE) is a valuable aromatic compound with favorable flavors and good properties, resulting in its widespread application in the cosmetic, food and medical industries. In this study, a mutant strain, AD032, was first obtained by adaptive evolution under 2-PE stress. Then, a fusion protein from the Ehrlich pathway, composed of tyrB from Escherichia coli, kdcA from Lactococcus lactis and ADH2 from Saccharomyces cerevisiae, was constructed and expressed. As a result, 3.14 g/L 2-PE was achieved using L-phenylalanine as a precursor. To further increase 2-PE production, L-glutamate oxidase from Streptomyces overexpression was applied for the first time in our research to improve the supply of α-ketoglutarate in the transamination of 2-PE synthesis. Furthermore, we found that the disruption of the pyruvate decarboxylase encoding gene PDC5 caused an increase in 2-PE production, which has not yet been reported. Finally, assembly of the efficient metabolic modules and process optimization resulted in the strain RM27, which reached 4.02 g/L 2-PE production from 6.7 g/L L-phenylalanine without in situ product recovery. The strain RM27 produced 2-PE (0.8 mol/mol) with L-phenylalanine as a precursor, which was considerably high, and displayed manufacturing potential regarding food safety and process simplification aspects. This study suggests that innovative strategies regarding metabolic modularization provide improved prospects for 2-PE production in food exploitation.

Functional studies of flaked and ground stone artefacts reveal starchy tree nut and root exploitation in mid-Holocene highland New Guinea

Ground stone technology for processing starchy plant foods has its origins in the late Pleistocene, with subsequent intensification and transformation of this technology coinciding with the global emergence of agriculture in the early Holocene. On the island of New Guinea, agriculture first emerges in the highland Wahgi Valley, potentially from c. 9 kya, and clearly evident by 6.5 kya. Approximately 400 km further east in the highland Ivane Valley, long-term occupation sequences span the Holocene and late Pleistocene, but there is currently no direct evidence for wetland agriculture. Here, we report rare evidence for ground stone implements from a secure mid-Holocene archaeological context in the Ivane Valley. The Joe’s Garden site has flaked and ground stone artefacts with significant starch assemblages dating to approximately 4.4 kya. We present the first empirical evidence for the function of stone bowls from a New Guinea highland setting. Usewear and residues indicate the grinding and pounding of endemic starch-rich plant foods. Geometric morphometric analysis of starch grains shows that at least two taxa were processed: Castanopsis acuminatissima (nut) and Pueraria lobata (tuber). This regional example adds to our understanding of the trajectories of diverse plant food exploitation and ground stone technology development witnessed globally in the Holocene.

Insectivory characteristics of the Japanese marten (Martes melampus): a qualitative review

Insects are rich in protein and thus are important substitute foods for many species of generalist feeders. This study reviews insectivory characteristics of the Japanese marten (Martes melampus) based on current literature. Across the 16 locations (14 studies) in the Japanese archipelago, a total of 80 different insects (including those only identified at genus, family, or order level) were listed as marten food, 26 of which were identified at the species level. The consumed insects were categorised by their locomotion types, and the Japanese martens exploited not only grounddwelling species, but also arboreal, flying, and underground-dwelling insects, taking advantage of their arboreality and ability of agile pursuit predation. Notably, immobile insects such as egg mass of Mantodea spp, as well as pupa/larvae of Vespula flaviceps and Polistes spp. from wasp nests were consumed by the Japanese marten in multiple study areas. This review shows dietary generalism (specifically ‘food exploitation generalism’) of the Japanese marten in terms of non-nutritive properties (i.e., locomotion ability of prey).

Effect of leaf decomposition stage and water temperature on fragmentation activity of a shredder invertebrate species in lotic ecosystems

ABSTRACT The attractiveness of a given leaf detritus to invertebrates depends on the chemical composition, physical structure, stage of microbial colonization and decomposition level. In addition to the leaf detritus quality, water temperature also affects organic matter cycling in aquatic environments. In this context, the objectives of this study were: i) to increase knowledge about the role of invertebrate shredders on fragmenting senescent, conditioned senescent and green leaves of Richeria grandis Vahl. (Phyllanthaceae) under gradual temperature rise and check leaf mass loss; ii) to verify the preference of Phylloicus sp. (Trichoptera) for leaves for larval case production. The experiment I consisted of three treatments with different water temperatures: 20°C, 24°C and 28°C. In the experiment II, we added 10 discs of green leaves of R. grandis and two shredder invertebrates (Phylloicus sp.) to each aquarium. Leaf mass loss in the presence or absence of fragmentation was not significantly influenced by differences in the intraspecific quality of the detritus or temperature. Intraspecific quality of resources mixed with green leaves can lead to increased contact of phenolic content on senescent leaves, leading to a similarity in food exploitation by invertebrates. However, the production of larval cases by Phylloicus sp. seems to be dependent on the resistance presented by the resource rather than the phenolic content, thus leading the shredders to use significantly more senescent detritus, regardless temperature.

Stable Isotopic Detection of Manual Intervention Among the Faunal Assemblage from a Majiayao Site in NW China

Faunal remains from Shannashuzha in Minxian County, Gansu Province, China were isotopically analyzed to understand animal husbandry, and thus human subsistence strategy, during the Majiayao culture (5200–4800 cal yr BP) period. Stable carbon isotopic results reveal that only two pig samples clearly show a C4-dominated diet with a mean δ13C value of –8.5‰, which possibly indicated controlled feeding practices by human beings. No other significant manual intervention can be observed among the remaining samples, suggesting that both wild and domesticated meat sources were used at Shannashuzha. Statistically, Bos are indistinguishable from Cervidae based solely on isotopic results, suggesting that Bos may have remained in wild form during the Majiayao culture period. The presence of hare/rabbit, bamboo rat, and badger reflects the diversified food exploitation behavior.

Impact of Interference Competition on Exploration and Food Exploitation in the AntLasius niger

Competition acts as a major force in shaping spatially and/or temporally the foraging activity of ant colonies. Interference competition between colonies in particular is widespread in ants where it can prevent the physical access of competitors to a resource, either directly by fighting or indirectly, by segregating the colony foraging areas. Although the consequences of interference competition on ant distribution have been well studied in the literature, the behavioral mechanisms underlying interference competition have been less explored. Little is known on how ants modify their exploration patterns or the choice of a feeding place after experiencing aggressive encounters. In this paper, we show that, at the individual level, the aphid-tending antLasius nigerreacts to the presence of an alien conspecific through direct aggressive behavior and local recruitment in the vicinity of fights. At the colony level, however, no defensive recruitment is triggered and the “risky” area where aggressive encounters occur is not specifically avoided during further exploration or food exploitation. We discuss how between-species differences in sensitivity to interference competition could be related to the spatial and temporal predictability of food resources at stake.