Papers by Carlos Alvarado
Food Technology and …, 2006
Biotehnološka proizvodnja i novija primjena mliječne kiseline Sažetak Mliječna se kiselina upotre... more Biotehnološka proizvodnja i novija primjena mliječne kiseline Sažetak Mliječna se kiselina upotrebljava u prehrambenoj, kozmetičkoj, farmaceutskoj i kemijskoj industriji te sve više i kao monomer za proizvodnju biorazgradljive (poli)mliječne kiseline. Mliječna se kiselina može proizvesti biotehnološkim procesom ili kemijskom sintezom. U novije se vrijeme sve više koristi biotehnološki postupak zbog zaštite okoliša i ograničene količine petrokemijskih izvora. Na različite načine pokušala se proizvesti mliječna kiselina iz jeftinih sirovina. U ovom su radu prikazani mikroorganizmi i sirovine za proizvodnju mliječne kiseline, njezina biotehnološka proizvodnja te načini primjene, a osobito najnovija istraživanja. Također se raspravlja o mogućnosti i ekonomskoj važnosti primjene mliječne kiseline u budućnosti.
Plant Physiology and Biochemistry, 2007
Candidate traits for drought tolerance were targeted by analyzing water stress responses in two m... more Candidate traits for drought tolerance were targeted by analyzing water stress responses in two moderately drought-tolerant native Andean potato clones, SA2563 and Sullu (Solanum tuberosum L. subsp, andigena (Juz, Bukasov) Hawkes) under field conditions. SA2563 exhibited increased root growth under drought, while Sullu retained a higher relative leaf water content. Gene expression profiling using the TIGR 10 K microarray revealed 1713 significantly differentially expressed genes, 186 of these genes were up-regulated in both clones. In addition to these commonly up-regulated genes, each clone induced a specific gene set in response to drought. Gene expression and metabolite analysis pinpointed candidate traits for drought tolerance present either in one or both of the clones under investigation. These traits included osmotic adjustment, changes in carbohydrate metabolism, membrane modifications, strengthening of cuticle and cell rescue mechanisms, such as detoxification of oxygen radicals and protein stabilization. Many of the up-regulated genes have been identified previously in laboratory studies on model plants using shock treatments, and the present study confirms the importance of these factors under field conditions.
Polyphenols represent a large family of plant secondary metabolites implicated in the prevention ... more Polyphenols represent a large family of plant secondary metabolites implicated in the prevention of various diseases such as cancers and cardiovascular diseases. The potato is a significant source of polyphenols in the human diet. In this study, we examined the expression of thirteen genes involved in the biosynthesis of polyphenols in potato tubers using real-time RT-PCR. A selection of five field grown native Andean cultivars, presenting contrasting polyphenol profiles, was used. Moreover, we investigated the expression of the genes after a drought exposure. We concluded that the diverse polyphenolic profiles are correlated to variations in gene expression profiles. The drought-induced variations of the gene expression was highly cultivar-specific. In the three anthocyanin-containing cultivars, gene expression was coordinated and reflected at the metabolite level supporting a hypothesis that regulation of gene expression plays an essential role in the potato polyphenol production. We proposed that the altered sucrose flux induced by the drought stress is partly responsible for the changes in gene expression. This study provides information on key polyphenol biosynthetic and regulatory genes, which could be useful in the development of potato varieties with enhanced health and nutritional benefits.
The effects of drought stress on dietary antioxidant and glycoalkaloid contents in potato tubers ... more The effects of drought stress on dietary antioxidant and glycoalkaloid contents in potato tubers were investigated using a selection of five native Andean cultivars. Both freshly harvested and 4 month-stored tubers were analyzed. Responses to drought stress were highly cultivar-specific. The antioxidant contents of the yellow tuber-bearing cultivars (Sipancachi and SS-2613) were weakly affected by the drought treatment, whereas the pigmented cultivars demonstrated highly cultivar-dependent variations. A drastic reduction of anthocyanins and other polyphenols was revealed in the red- (Sullu) and purple-fleshed (Guincho Negra) cultivars, whereas an increase was shown in the purple-skinned and yellow-fleshed cultivar (Huata Colorada). The hydrophilic antioxidant capacity (evaluated by Folin-Ciocalteu and H-oxygen radical absorbance capacity assays) was highly correlated with the polyphenol content and followed, therefore, the same behavior upon drought. Carotenoid contents, including beta-carotene, as well as vitamin E, tended to increase or remain stable following drought exposure, except for the cultivar Sullu, in which the level of these lipophilic antioxidants was decreased. Vitamin C contents were not affected by drought with the exception of Guincho Negra, in which the level was increased. These variations of health-promoting compounds were associated with increased or stable levels of the toxic glycoalkaloids, alpha-solanine and alpha-chaconine. Storage at 10 degrees C for 4 months tended to decrease the concentrations of all dietary antioxidants, except those of vitamin E. This storage also reduced the drought-induced variations observed in freshly harvested tubers. These results were discussed in terms of their implications for human diet and health as well as in plant stress defense mechanisms.
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Papers by Carlos Alvarado