5-CQA and Mangiferin, Two Leaf Biomarkers of Adaptation to Full Sun or Shade Conditions in Coffea arabica L.

Phenolic compounds are involved in plant response to environmental conditions and are highly present in leaves of Coffea arabica L., originally an understory shrub. To increase knowledge of C. arabica leaf phenolic compounds and their patterns in adaptation to light intensity, mature leaves of Ethiopian wild accessions, American pure lines and their relative F1 hybrids were sampled in full sun or under 50% shade field plots in Mexico and at two contrasting elevations in Nicaragua and Colombia. Twenty-one phenolic compounds were identified by LC-DAD-MS2 and sixteen were quantified by HPLC-DAD. Four of them appeared to be involved in C. arabica response to light intensity. They were consistently more accumulated in full sun, presenting a stable ratio of leaf content in the sun vs. shade for all the studied genotypes: 1.6 for 5-CQA, F-dihex and mangiferin and 2.8 for rutin. Moreover, 5-CQA and mangiferin contents, in full sun and shade, allowed for differentiating the two genetic groups of Ethiopian wild accessions (higher contents) vs. cultivated American pure lines. They appear, therefore, to be potential biomarkers of adaptation of C. arabica to light intensity for breeding programs. We hypothesize that low 5-CQA and mangiferin leaf contents should be searched for adaptation to full-sun cropping systems and high contents used for agroforestry systems.

A comparative study on the potential of epiphytic yeasts isolated from tropical fruits to produce flavoring compounds.

In recent years, there has been an increasing interest in identifying and characterizing the yeast flora associated with diverse types of habitat because of the many potential desirable technological properties of these microorganisms, especially in food applications. In this study, a total of 101 yeast strains were isolated from the skins of tropical fruits collected in several locations in the South West Indian Ocean. Sequence analysis of the D1/D2 domains of the large subunit (LSU) ribosomal RNA gene identified 26 different species. Among them, two species isolated from the skins of Cape gooseberry and cocoa beans appeared to represent putative new yeast species, as their LSU D1/D2 sequence was only 97.1% and 97.4% identical to that of the yeasts Rhodotorula mucilaginosa and Candida pararugosa, respectively. A total of 52 Volatile Organic Compounds (VOCs) were detected by Head Space Solid Phase Micro Extraction coupled to Gas Chromatography and Mass Spectroscopy (HS-SPME-GC/MS) from the 26 yeast species cultivated on a glucose rich medium. Among these VOCs, 6 uncommon compounds were identified, namely ethyl but-2-enoate, ethyl 2-methylbut-2-enoate (ethyl tiglate), ethyl 3-methylbut-2-enoate, 2-methylpropyl 2-methylbut-2-enoate, butyl 2-methylbut-2-enoate and 3-methylbutyl 2-methylbut-2-enoate, making them possible yeast species-specific markers. In addition, statistical methods such as Principal Component Analysis allowed to associate each yeast species with a specific flavor profile. Among them, Saprochaete suaveolens (syn: Geotrichum fragrans) turned to be the best producer of flavor compounds, with a total of 32 out of the 52 identified VOCs in its flavor profile.

Antimicrobial effects of essential oils of Cinnamosma fragrans on the bacterial communities in the rearing water of Penaeus monodon larvae.

Farmed shrimps are vectors of various Vibrio species that are considered a potential health hazard. Previous study has shown that Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus dominated in the water and larval samples of shrimp hatchery (Randrianarivelo et al. 2010 ). The effects of two essential oils (EOs) of Cinnamosma fragrans, an endemic plant to Madagascar (B8: linalool-type and B143: 1,8-cineole-type), were determined on the total heterotrophic aerobic bacteria and the Vibrio concentrations in the rearing water of Penaeus monodon hatchery. The assays took place in OSO Farming's shrimp hatchery in Madagascar. EOs were directly added to the water tank. The bacterial concentrations of water tank were assessed on marine agar and thiosulfate citrate bile sucrose agar. The larvae culture corresponded to four replicates each of B8, B143, erythromycin (E), and control (oil and antibiotic free). The bacterial concentration of the rearing water in B8, B143, and antibiotic (E) tanks were significantly lower (p < 0.05) than in the control. Further, there was no significant difference (p > 0.05) between the three treatments B8, B143, and E. This study demonstrated that both EOs of C. fragrans, like antibiotic, inhibited bacterial growth in the rearing water of P. monodon larvae. The potential of C. fragrans EO to control the bacterial load in in vivo conditions of P. monodon hatchery makes it a relevant option for producers to minimize risk of Vibrio growth in the rearing water of larvae, which is the primary source of colonization of shrimp larvae.

Osmotic stress, glucose transport capacity and consequences for glutamate overproduction in Corynebacterium glutamicum.

Glucose uptake by Corynebacterium glutamicum is predominantly assured by a mannose phosphotransferase system (PTS) with a high affinity for glucose (Km=0.35 mM). Mutants selected for their resistance to 2-deoxyglucose (2DG) and lacking detectable PEP-dependent glucose-transporting activity, retained the capacity to grow on media in which glucose was the only carbon and energy source, albeit at significantly diminished rates, due to the presence of a low affinity (Ks=11 mM) non-PTS uptake system. During growth in media of different osmolarity, specific rates of glucose consumption and of growth of wild type cells were diminished. Cell samples from these cultures were shown to possess similar PTS activities when measured under standard conditions. However, when cells were resuspended in buffer solutions of different osmolarity measurable PTS activity was shown to be dependent upon osmolarity. This inhibition effect was sufficient to account for the decreased rates of both sugar uptake and growth observed in fermentation media of high osmolarity. The secondary glucose transporter was, however, not influenced by medium osmolarity. During industrial fermentation conditions with accumulation of glutamic acid and the corresponding increase in medium osmolarity, similar inhibition of the sugar transport capacity was observed. This phenomenon provokes a major process constraint since the decrease in specific rates leads to an increasing proportion of sugar catabolised for maintenance requirements with an associated decrease in product yields.