Effect of soaking conditions on properties of flour from sweet potato slices

Native flour of sweet potato has limited industrial applications. This study investigated effect of soaking sweet potato root in hot water and citric acid concentrations on flour properties. Sweet potato root was soaked at temperatures of 50oC, 60oC and 70oC for 2 h; citric acid concentrations of 1%, 3% and 5% for 1 h, and combination of best samples in each of the first two modification treatments in 50:50 proportions. Treated root was processed into flour using standard procedures. Proximate, functional and pasting properties of the flours were determined using standard methods. The flour was used as major ingredient in production of baked snacks. Treatments had significant effect on proximate, functional and pasting properties of the flour. Moisture content ranged from 6.5 to 9.7%, protein content 1.6 to 3.0%, ash content 0.1 to 3.15%, fiber content 3.6 to 4.2%, and carbohydrate content 82.1 to 84.7%. Water and oil absorption capacities ranged from 2.2 to 3.0 ml/g and 0.8 g/ml to 1.8 g/ml respectively, swelling power (4.32 to 9.23 g/g) and bulk density (0.77 to 0.95 g/ml). Snack produced with flour gotten from 60oC soaked root for 2 h was best in sensory ratings.

Optimization of saccharification prospective from starch of sweet potato roots through acid-enzyme hydrolysis: structural, chemical and elemental profiling

The sweet potato root, a potent source of starch which is being considered as an efficient alternative for fuel ethanol production in recent times. The starchy substrate needs to be subsequently dextrinized and saccharified so as to enhance the utilization of its carbohydrates for ethanol production. In the present investigation, acid-enzyme process was conducted for the dextrinization and saccharification of sweet potato root flour (SPRF). The best optimized condition for dextrinization was achieved with an incubation period of 60 min, temperature 100 ºC and 1M HCl. However, for saccharification, the best result was obtained with an incubation of 18 h, pH 4, temperature 65 ºC and 1000 U concentration of Palkodex®. After the dextrinization process, maximum concentrations of total sugar and hydroxymethylfurfural (HMF) [380.44 ± 3.17 g/kg and 13.28 ± 0.25 mg/g, respectively] were released. Nevertheless, after saccharification, 658.80 ± 7.83 g/kg of total sugar was obtained which was about 73% more than that of dextrinization. After successful dextrinization and saccharification, the structural, chemical and elemental analysis were investigated using techniques such as scanning electron microscopy (SEM), Fourier-transforms infrared spectroscopy (FTIR) and energy-dispersive X-ray fluorescence spectrophotometer (EDXRF), respectively. Effective hydrolysis was demonstrated in thin layer chromatography (TLC) where the HCl was able to generate monomeric sugar such as glucose and maltose. On the other hand, only glucose is synthesized on the mutual effect of HCl and Palkodex®. The SEM findings indicate that the rough structure of both dextrinized and saccharified sample was gained due to the vigorous effect of both acid and enzyme subsequently. The saccharified SPRF when subjected to fermentation with Saccharomyces cerevisiae and Zymomonas mobilis separately, it was observed that Z. mobilis produced more stretching vibration of –OH than S. cerevisiae, which evidenced the better production of bioethanol. Additionally, evaluation of the influence of S. cerevisiae and Z. mobilis through elemental analysis revealed upsurge in the concentrations of S, Cl, Ca, Mn, Fe and Zn and decline in the concentrations of P, K and Cu in the fermented residue of S. cerevisiae and Z. mobilis, however, Z. mobilis showed little more variation than that of S. cerevisiae.

Monosaccharide constituents of potato root exudate influence hatching of the white potato cyst nematode

Plants secrete a large array of compounds into the rhizosphere to facilitate interactions with their biotic environment. Some of these exuded-compounds stimulate the hatching of obligate plant-parasitic nematodes, ultimately leading to a detrimental effect on the host plant. Determining these cues can help to provide new mechanisms for control and aid nematode management schemes. Here we show that glucose, fructose and arabinose, which are all present in potato root exudate (PRE), induce hatching of white potato cyst nematode (Globodera pallida) eggs whereas five other PRE-sugars had no effect. Although these monosaccharides resulted in significant hatching none induced the same level as PRE, suggesting that other components, possibly in combination, contribute to stimulation of nematode hatching. Glucose, but not arabinose or fructose, was also observed to attract juvenile G. pallida, indicating that these hatch-inducing components can have different roles in different stages of the life cycle. Applying a solution of these monosaccharides to G. pallida-infested soil pre-potato planting initiated hatching in the absence of a host. Host absence resulted in nematode mortality and a reduction in the G. pallida population. Therefore, subsequent invasion of the crop post-planting was also reduced, compared to untreated soil. Our data suggest that monosaccharide components of PRE play an important role in the hatching and attraction of G. pallida. As a result the hatch-inducing monosaccharides can be applied as a pre-planting treatment to induce hatching and reduce subsequent infection rates.

The influence of growth stage on the structure and formation of fungal microbiota in potato root

In the potato root, Fusarium populations greatly increase during the flowering stage of growth. At senescence, a decrease in their share and a significant surge in Monographella spp. is observed.

Proteomic analysis of potato responding to the invasion of Ralstonia solanacearum UW551 and its type III secretion system mutant

The infection of potato with Ralstonia solanacearum (R. solanacearum) UW551 gives rise to bacterial wilt disease via colonization of roots. The Type III Secretion System (T3SS) is a determinant factor for the pathogenicity of R. solanacearum. To fully understand perturbations in potato by R. solanacearum Type III Effectors(T3Es), we use proteomics to measure differences in potato root protein abundance after inoculation with R. solanacearum UW551 and T3SS mutant (UW551△HrcV). We identified 21 differentially accumulated proteins (DAPs). Compared to inoculation with UW551△HrcV, ten proteins showed significantly lower abundance in potato roots after inoculation with UW551, indicating those proteins were significantly down-regulated by T3Es during the invasion. To identify their functions in immunity, we silenced those genes in Nicotiana benthamiana and tested the resistance of the silenced plants to the pathogen. Results showed that miraculin, HBP2, TOM20 contribute to immunity to R. solanacearum. In contrast, PP1 contribute to susceptibility. Notably, none of four downregulated proteins (HBP2, PP1, HSP22, TOM20) were downregulated at the transcriptional level, suggesting that they were significantly down-regulated at the post-transcriptional level. We further co-expressed those four proteins with thirty-three core T3Es. To our surprise, multiple effectors were able to significantly decrease the sudied protein abundances. In conclusion, our data showed T3Es of R. solanacearum could subvert potato root immune-related proteins in a redundant manner.

Effects of StAAP1 and StAAP8 in Potato ATFs Transcription Factor Family on Plant Development

Background: Amino acid transporters mediated the transport of various amino acids in plants, which were essential for plant growth and development. ATFs (the amino acid transporter family) was one of amino acid transporters in plants and AAPs (amino acid permease) subfamily belongs to the ATFs family.Results: In this research, eight AAP genes were identified in the potato and divided into two subgroups. The first subgroup is the StAAP gene containing six microporous transport channels (Pore-lining), and the second subgroup are the StAAP gene containing seven microporous transport channels. The subcellular location and overexpression vectors were built by StAAP1 and StAAP8. The results indicated these two genes were localized on the cell membrane. Observing the phenotype of the transgenic plants, StAAP1 and StAAP8 promoted the growth of leaves, StAAP1 changed the shape of tubers and enhanced their weight and StAAP8 was no significant influence in tubers but decreased the weight a little.Conclusions: In this study, the expression pattern showed StAAP8 might regulate the transport of amino acids in potato roots and affect the osmotic potential of potato root cells. Thereby, the tolerance of plants to abiotic stress and StAAP1 and StAAP8 promote the amino acid transport into leaves and StAAP1 had effected on tuber development and StAAP8 might resist the weight of tubers.