Rate Of Starch Degradation Research Articles

Integration of engineering microbial consortium and boosting extracellular amylase of B. amyloliquefaciens for intensifying bioconversion of food waste into lipopeptides

Lipopeptides possess significant antifungal activity and serve as eco-friendly biopesticides. However, their widespread application is limited by exorbitant production costs and low yields. Food waste emerges as a promising substrate for lipopeptide production. To efficiently harness the starch in food waste during bioconversion it into lipopeptides, the engineered Bacillus amyloliquefaciens HM618, constructed by knocking out multiple extracellular proteolytic enzyme genes (aprE, nprE, vpr, and epr) and overexpressing gene amyA with Phag promoter, capable of producing both high-level extracellular amylase and lipopeptides. It was found that the recombinant B. amyloliquefaciens HM3–5 in the pure culture containing starch exhibited notable amylase activity about 17046.37 U/mL, a total of 2530.72 mg/L lipopeptides, and 80.02 % degradation rate of starch. Considering the crucial roles of fatty acids and amino acids precursors in lipopeptide synthesis, these engineered B. amyloliquefaciens producing higher-level extracellular amylase, Yarrowia lipolytica producing fatty acids, and Corynebacterium glutamicum releasing proline and serine were integrated to construct an artificial consortium for efficiently bio-converting food waste into lipopeptides. After optimized inoculation times and ratios of these engineered strains, the levels of surfactin, fengycin, and iturin A in the four-strains artificial consortium during food waste bioconversion reached 8690.67, 635.83, and 74.19 mg/L, respectively. The total lipopeptides in the four-strain artificial consortium reached 9400.69 mg/L, 2.38-fold increase compared to that in the pure culture of strain HM3–5. Furthermore, the degradation efficiencies of starch and oil in food waste were 96.41 % and 98.35 %, respectively. This work provides a new strategy for efficiently bio-transforming food waste into lipopeptides.

Assessing the impacts of genetic defects on starch metabolism in Arabidopsis plants using the carbon homeostasis model.

Starch serves as an important carbon storage mechanism for many plant species, facilitating their adaptation to the cyclic variations in the light environment, including day-night cycles as well as seasonal changes in photoperiod. By dynamically adjusting starch accumulation and degradation rates, plants maintain carbon homeostasis, enabling continuous growth under fluctuating environmental conditions. To understand dynamic nature of starch metabolism at the molecular level, it is necessary to integrate empirical knowledge from genetic defects in specific regulatory pathways into the dynamical system of starch metabolism. To achieve this, we evaluated the impact of genetic defects in the circadian clock, sugar sensing and starch degradation pathways using the carbon homeostasis model that encompasses the interplay between these pathways. Through the collection of starch metabolism data from 10 Arabidopsis mutants, we effectively fitted the experimental data to the model. The system-level assessment revealed that genetic defects in both circadian clock components and sugar sensing pathway hindered the appropriate adjustment of the starch degradation rate, particularly under long-day conditions. These findings not only confirmed the previous empirical findings but also provide the novel insights into the role of each gene within the gene regulatory network on the emergence of carbon homeostasis.

Comparison between IAD and other maturity indices in nine commercially grown apple cultivars

To maintain storage potential as long as possible, it is important to harvest fruit at optimal maturity. Different maturity indices have been developed, including flesh firmness, soluble solids content, starch degradation, ethylene production, and respiration rate. However, many of them are destructive, time consuming, and may be require some laboratory equipment to perform. The portable device DA-meter (measuring index of absorption difference; IAD) can monitor the chlorophyll decline non-destructively in the field, and could potentially save time. To evaluate the IAD in comparison with other maturity indices, nine common commercial cultivars of apple were investigated in a three-year trial. Correlations between IAD and other maturity indices, especially starch degradation and ripening index by Streif were strong in most cultivars, though variation between years lead to weaker correlations were found last year of the trial. The strongest correlations were found between IAD and harvest date showing that IAD decreased with time in all investigated cultivars. Comparison between IAD and ripening index by Streif showed in some cases that the two indices decreased at the same time, suggesting that IAD could be used to monitor maturity when it is rapid. The suitability to use IAD as a maturity index seems to be cultivar-dependent. For cultivars having a more consistent pattern between years in the decrease of IAD, combined with relatively low variation in IAD at any given time, it could be a good complement to other commonly used maturity indices.

Solid-State Fermentation Improves Tobacco Leaves Quality via the Screened Bacillus subtilis of Simultaneously Degrading Starch and Protein Ability.

The process of tobacco aging plays a significant role in enhancing the smoking experience by improving the flavor and quality of tobacco leaves.During natural aging, the metabolic activity of the microbes on the surface oftobacco leaves will be greatly changed. Besides, starch and protein are two of the main macromolecularcompounds causing the poor smoking quality of tobacco leaves which to be degraded for better tobaccoquality. In this study, a bacterium with the simultaneously degrading ability of starch (degradation rate of 33.87%) and protein (degradation rate of 20%) has been screened out from high-class tobacco leaf and then inoculated into low-class tobacco leaf by solid-state fermentation for quality improvement. The changes in components related to carbon and nitrogen showed that the strain had an obvious effect on the quality improvement of tobacco leaves. After that, GC-MS analyses displayed the volatile flavor compounds which become rich and the flavor has been improved. It has been proved that inoculation solid-state fermentation by dominant strain could improve tobacco quality, as well as instead of the traditional natural aging process which greatly shortens the aging process. The work also offers a helpful strategy for solid-state products for deep fermentation.

Starch degradation in the bean fruit pericarp is characterized by an increase in maltose metabolism.

The bean fruit pericarp accumulates a significant amount of starch, which starts to be degraded 20 days after anthesis (DAA) when seed growth becomes exponential. This period is also characterized by the progressive senescence of the fruit pericarp. However, the chloroplasts maintained their integrity, indicating that starch degradation is a compartmentalized process. The process coincided with a transient increase in maltose and sucrose levels, suggesting that β-amylase is responsible for starch degradation. Starch degradation in the bean fruit pericarp is also characterized by a large increase in starch phosphorylation, as well as in the activities of cytosolic disproportionating enzyme 2 (DPE2, EC 2.4.1.25) and glucan phosphorylase (PHO2, EC 2.4.1.1). This suggests that the rate of starch degradation in the bean fruit pericarp 20 DAA is dependent on the transformation of starch to a better substrate for β-amylase and the increase in the rate of cytosolic metabolism of maltose.

Phosphorylation of DPE2 at S786 partially regulates starch degradation

In plants, transitory starch is synthetized during the day and degraded at night to provide the continuous carbon needed for growth and development. Starch metabolism is highly coordinated, as the starch degradation rate must be coupled to the amount of starch synthetized during the day. Maltose is one of the chloroplastic products obtained from starch degradation, and maltose is exported to the cytosol where disproportionating enzyme-2 (DPE2) is responsible for its metabolism. The amount of DPE2 remained unchanged throughout the day, but its activity notably increased at the end of the day (7 p.m.), suggesting that posttranslational modification drives the mechanism underlying the regulatory activity of this enzyme. Sucrose nonfermenting-related kinase-1 (SnRK1), a protein kinase that controls the activity of several metabolic enzymes, was able to interact and phosphorylate DPE2 at three different residues localized in the α-glucanotransferase domain. This phosphorylation acts as a positive regulator of DPE2, increasing its activity. Complementation of dpe2-deficient mutants with the wild-type (WT) and S786A forms of DPE2 showed that the nonphosphorylated form of DPE2 only partially restored starch degradation, suggesting that phosphorylation at S786 is involved in enzyme regulation.

Effects of nitrate sources on in vitro methane production and ruminal fermentation parameters in diets differing in starch degradability

We evaluated the effects of nitrate (NO3−) sources supplemented in diets differing in starch degradability on in vitro DM and NDF degradability, methane (CH4) and nitrous oxide (N2O) production, and ruminal fermentation parameters. The experiment followed a randomized complete block design with a 5 × 2 factorial arrangement. Treatments were five sources of non-protein nitrogen (NPN), including urea (URE), potassium NO3− (PON), calcium-ammonium NO3− (CAN), dolomite-ammonium NO3− (DAN), and ammonium NO3− (AMN), supplemented on total-mixed rations constituted with either high-moisture corn (HMC) or dry rolled corn (DRC).In vitro DM and NDF degradability, gas production, CH4 and N2O emissions, and VFA and ammonia-N concentrations were evaluated after 12 and 24 h of incubation. All experimental procedures were repeated in three runs and run was used as a blocking factor.In vitro DM and NDF degradability were not affected by NO3− sources. Nitrate supplementation decreased CH4 production (mmol/ g DM degraded) by 23 % compared to URE regardless of the source. Concomitantly, N2O emissions were increased by all NO3− sources, with the highest amount (1.24 ppm) for PON after 24 h of incubation. High-moisture corn diets improved in vitro DM and NDF degradability, increased propionate production, and consequently reduced acetate: propionate ratio. Methane production (mmol/g DM degraded) was reduced by 34 % in HMC diets after 24 h of incubation when compared with DRC diets. No interactions were observed between NO3− and starch sources in all the evaluated parameters, leading us to conclude that NO3− sources acted independently at reducing CH4 production, regardless of the rate of ruminal starch degradation.

A Review: Plant Carbohydrate Types-The Potential Impact on Ruminant Methane Emissions.

Carbohydrates are the major component of most ruminant feeds. The digestion of carbohydrates in the rumen provides energy to the ruminants but also contributes to enteric methane (CH4) emissions. Fresh forage is the main feed for grazing ruminants in temperate regions. Therefore, this review explored how dietary carbohydrate type and digestion affect ruminant CH4 emissions, with a focus on fresh forage grown in temperate regions. Carbohydrates include monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Rhamnose is the only monosaccharide that results in low CH4 emissions. However, rhamnose is a minor component in most plants. Among polysaccharides, pectic polysaccharides lead to greater CH4 production due to the conversion of methyl groups to methanol and finally to CH4. Thus, the degree of methyl esterification of pectic polysaccharides is an important structural characteristic to better understand CH4 emissions. Apart from pectic polysaccharides, the chemical structure of other polysaccharides per se does not seem to affect CH4 formation. However, rumen physiological parameters and fermentation types resulting from digestion in the rumen of polysaccharides differing in the rate and extent of degradation do affect CH4 emissions. For example, low rumen pH resulting from the rapid degradation of readily fermentable carbohydrates decreases and inhibits the activities of methanogens and further reduces CH4 emissions. When a large quantity of starch is supplemented or the rate of starch degradation is low, some starch may escape from the rumen and the escaped starch will not yield CH4. Similar bypass from rumen digestion applies to other polysaccharides and needs to be quantified to facilitate the interpretation of animal experiments in which CH4 emissions are measured. Rumen bypass carbohydrates may occur in ruminants fed fresh forage, especially when the passage rate is high, which could be a result of high feed intake or high water intake. The type of carbohydrates affects the concentration of dissolved hydrogen, which consequently alters fermentation pathways and finally results in differences in CH4 emissions. We recommend that the degree of methyl esterification of pectic polysaccharides is needed for pectin-rich forage. The fermentation type of carbohydrates and rumen bypass carbohydrates should be determined in the assessment of mitigation potential.

Rising rates of starch degradation during daytime and trehalose 6-phosphate optimize carbon availability.

Many plants, including Arabidopsis (Arabidopsis thaliana), accumulate starch in the light and remobilize it to support maintenance and growth at night. Starch synthesis and degradation are usually viewed as temporally separate processes. Recently, we reported that starch is also degraded in the light. Degradation rates are generally low early in the day but rise with time. Here, we show that the rate of degradation in the light depends on time relative to dawn rather than dusk. We also show that degradation in the light is inhibited by trehalose 6-phosphate, a signal for sucrose availability. The observed responses of degradation in the light can be simulated by a skeletal model in which the rate of degradation is a function of starch content divided by time remaining until dawn. The fit is improved by extension to include feedback inhibition of starch degradation by trehalose 6-phosphate. We also investigate possible functions of simultaneous starch synthesis and degradation in the light, using empirically parameterized models and experimental approaches. The idea that this cycle buffers growth against falling rates of photosynthesis at twilight is supported by data showing that rates of protein and cell wall synthesis remain high during a simulated dusk twilight. Degradation of starch in the light may also counter over-accumulation of starch in long photoperiods and stabilize signaling around dusk. We conclude that starch degradation in the light is regulated by mechanisms similar to those that operate at night and is important for stabilizing carbon availability and signaling, thus optimizing growth in natural light conditions.

Reduced auxin signalling through the cyclophilin gene DIAGEOTROPICA impacts tomato fruit development and metabolism during ripening.

Auxin is an important hormone playing crucial roles during fruit growth and ripening; however, the metabolic impact of changes in auxin signalling during tomato (Solanum lycopersicum L.) ripening remains unclear. Here, we investigated the significance of changes in auxin signalling during different stages of fruit development by analysing changes in tomato fruit quality and primary metabolism using mutants with either lower or higher auxin sensitivity [diageotropica (dgt) and entire mutants, respectively]. Altered auxin sensitivity modifies metabolism, through direct impacts on fruit respiration and fruit growth. We verified that the dgt mutant plants exhibit reductions in fruit set, total fruit dry weight, fruit size, number of seeds per fruit, and fresh weight loss during post-harvest. Sugar accumulation was associated with delayed fruit ripening in dgt, probably connected with reduced ethylene levels and respiration, coupled with a lower rate of starch degradation. In contrast, despite exhibiting parthenocarpy, increased auxin perception (entire) did not alter fruit ripening, leading to only minor changes in primary metabolism. By performing a comprehensive analysis, our results connect auxin signalling and metabolic changes during tomato fruit development, indicating that reduced auxin signalling led to extensive changes in sugar concentration and starch metabolism during tomato fruit ripening.

A dominant mutation in β-AMYLASE1 disrupts nighttime control of starch degradation in Arabidopsis leaves.

Arabidopsis (Arabidopsis thaliana) leaves possess a mechanism that couples the rate of nighttime starch degradation to the anticipated time of dawn, thus preventing premature exhaustion of starch and nighttime starvation. To shed light on the mechanism, we screened a mutagenized population of a starvation reporter line and isolated a mutant that starved prior to dawn. The mutant had accelerated starch degradation, and the rate was not adjusted to time of dawn. The mutation responsible led to a single amino acid change (S132N) in the starch degradation enzyme BETA-AMYLASE1 (BAM1; mutant allele named bam1-2D), resulting in a dominant, gain-of-function phenotype. Complete loss of BAM1 (in bam1-1) did not affect rates of starch degradation, while expression of BAM1(S132N) in bam1-1 recapitulated the accelerated starch degradation phenotype of bam1-2D. In vitro analysis of recombinant BAM1 and BAM1(S132N) proteins revealed no differences in kinetic or stability properties, but in leaf extracts, BAM1(S132N) apparently had a higher affinity than BAM1 for an established binding partner required for normal rates of starch degradation, LIKE SEX FOUR1 (LSF1). Genetic approaches showed that BAM1(S132N) itself is likely responsible for accelerated starch degradation in bam1-2D and that this activity requires LSF1. Analysis of plants expressing BAM1 with alanine or aspartate rather than serine at position 132 indicated that the gain-of-function phenotype is not related to phosphorylation status at this position. Our results strengthen the view that control of starch degradation in wild-type plants involves dynamic physical interactions of degradative enzymes and related proteins with a central role for complexes containing LSF1.

Evaluating the relationship between in vitro and in situ starch degradation rates

Determining starch degradability is important because of its implicit relation to gut health, ruminal acidosis, energy availability, feed intake, and animal productivity. In vitro assays for protein and fiber degradability have been useful tools for ration formulation; however, analogous assessments of starch degradability have limited update. Our objective was to test how an enzymatic in vitro starch degradation assay compared with the in situ technique in terms of its ability to rank feeds based on their starch degradation rates. Samples of 19 livestock feeds were obtained from 4 feed mills and subjected to in vitro and in situ starch degradation analyses. Seven ruminally cannulated wethers on forage were used for the in situ procedure. In vitro starch degradation was assessed using an acetate buffer technique with modified enzymatic incubation times: amylase (AML) 5 min and amyloglucosidase (AMG) 10 min; AML 10 min and AMG 20 min; AML 15 min and AMG 30 min; AML 30 min and AMG 60 min; AML 45 min and AMG 90 min; and AML 60 min and AMG 120 min. In situ rates were determined using the Ørskov method and in vitro predicted rates calculated assuming exponential decay. Relationships were analyzed as a linear mixed-effects model with in situ degradation rate as the response variable and in vitro predicted degradation rate, initial free glucose, starch, crude protein, neutral detergent fiber (NDF), and fat content as fixed effects. Interactions between in vitro predicted degradation rate and the nutrient percentages were also included. Feed source was included as a random effect. In vitro predicted starch degradation rates ranged from 2.98% to 279%/h and in situ degradation rates ranged from 1.53% to 42.8%/h. A relationship between in vitro and in situ methods was observed when starch, fat, NDF, and initial free glucose content were accounted for. Interactions between in vitro predicted degradation rate and starch and NDF contents were also observed, suggesting that these nutrients may confound the relationship between in vitro and in situ starch degradation measurements. Removing the rapidly degradable starch fraction from in situ analysis calculations improved the strength of the relationship between in situ and in vitro starch degradation rate. This in vitro assay may prove more useful for determining relative rankings of starch degradation rates among different feedstuffs rather than serving as an alternative to the in situ method. Additional investigation into assay repeatability and comparisons with true in vivo estimations of starch degradation are needed to confirm the usefulness of this in vitro screening technique.

CRISPR-Cas9-mediated editing of starch branching enzymes results in altered starch structure in Brassica napus.

Starch branching enzymes (SBEs) are one of the major classes of enzymes that catalyze starch biosynthesis in plants. Here, we utilized the clustered regularly interspaced short palindromic repeats-CRISPR associated protein 9 (CRISPR-Cas9)-mediated gene editing system to investigate the effects of SBE mutation on starch structure and turnover in the oilseed crop Brassica napus. Multiple single-guide RNA (sgRNA) expression cassettes were assembled into a binary vector and two rounds of transformation were employed to edit all six BnaSBE genes. All mutations were heterozygous monoallelic or biallelic, and no chimeric mutations were detected from a total of 216 editing events. Previously unannotated gene duplication events associated with two BnaSBE genes were characterized through analysis of DNA sequencing chromatograms, reflecting the complexity of genetic information in B. napus. Five Cas9-free homozygous mutant lines carrying two to six mutations of BnaSBE were obtained, allowing us to compare the effect of editing different BnaSBE isoforms. We also found that in the sextuple sbe mutant, although indels were introduced at the genomic DNA level, an alternate transcript of one BnaSBE2.1 gene bypassed the indel-induced frame shift and was translated to a modified full-length protein. Subsequent analyses showed that the sextuple mutant possesses much lower SBE enzyme activity and starch branching frequency, higher starch-bound phosphate content, and altered pattern of amylopectin chain length distribution relative to wild-type (WT) plants. In the sextuple mutant, irregular starch granules and a slower rate of starch degradation during darkness were observed in rosette leaves. At the pod-filling stage, the sextuple mutant was distinguishable from WT plants by its thick main stem. This work demonstrates the applicability of the CRISPR-Cas9 system for the study of multi-gene families and for investigation of gene-dosage effects in the oil crop B. napus. It also highlights the need for rigorous analysis of CRISPR-Cas9-mutated plants, particularly with higher levels of ploidy, to ensure detection of gene duplications.

누룩으로부터 다양한 곰팡이의 선별과 전분 분해 활성을 이용한 동시당화발효

Various fungi were isolated from Korean traditional Nuruk and identified as ten types of fungal strains such as L. corymbifera, L. ramose, S. racemosum, R. oryzae, R. pusillus, M. racemosus, M. circinelloide, A. luchuensis, A. flavus, and A. fumigatus. Among them, four strains (A.fumigatus, A. luchuensis, A. flavus, and R. oryzae) exhibited relatively high glucoamylase activities. When the optimum reaction temperatures were verified for glucoamylase activity, A. fumigatus, A. luchuensis, and A. flavus showed the highest glucoamylase activity at 60℃, and R. oryzae showed the highest glucoamylase activity at 50℃. When simultaneous saccharification and fermentations were performed with yeast, R. oryzae showed the fastest starch degradation rate (1.17 ± 0.10 g/L·h) and the highest ethanol production (17.17 ± 1.46 g/L) for 72 hours.

Effect of drought stress on in situ ruminal starch degradation kinetics of corn for silage

The objective of this study was to determine the effect of drought stress on the in situ ruminal starch degradation kinetic parameters of corn for silage. Five commercial corn hybrids for silage were utilized. The experiment was designed as a split-plot within a randomized complete block design with 4 blocks. Eight plots were blocked and randomly subjected to a watered (W) or non-watered (NW) treatment. Within each block, plots were split into 5 sub-plots, to which 1 of the 5 corn hybrids were randomly assigned. Before planting, all plots were irrigated with 150 mm of water to ensure a consistent emergence of corn seedlings. After this pre-planting irrigation, NW plots were not irrigated ever again. After planting, W plots were irrigated with 75 mm of water when the crop showed 2 visible leaves, 6 visible leaves, and pre-tasseling and with 45 mm every week, thereafter, for a total of 8 weeks (360 mm post-tasseling). Three ears from each subplot were collected when corn crops were between the 1/4 and 3/4 milk-line stage of maturity. Kernels were shelled by hand and dried. The in situ ruminal starch degradability was determined on ground (4-mm) grain samples placed in Dacron porous bags. All bags were immersed within the rumen of 3 rumen-cannulated cows fed a totally mixed ration containing 32 % corn silage, 3 % alfalfa hay, and 65 % concentrate mix (DM basis). Bags were incubated for 0, 4, 8, 12, 24, and 48 h. Water stress did not affect the fraction of instantly degraded starch (203 mg/g), the fraction of potentially degraded starch (759 mg/g), the fraction of undegraded starch (38 mg/g), or the differential starch degradation rate (0.0669/h). Corn hybrids did not affect any of these degradation kinetic parameters and no interactions existed between irrigation treatment and corn hybrid. In conclusion, drought stress had no effect on the in situ ruminal starch degradability of corn for silage.

Effects of corn grain endosperm type and fineness of grind on site of digestion, ruminal digestion kinetics, and flow of nitrogen fractions to the duodenum in lactating dairy cows

Our objective was to evaluate effects of corn grain endosperm type and fineness of grind on feed intake, feeding behavior, and productive performance of lactating cows. Eight ruminally and duodenally cannulated Holstein cows in mid lactation (130 ± 42 d in milk; mean ± standard deviation) were used in a duplicated 4 × 4 Latin square design with 21-d periods. A 2 × 2 factorial arrangement of treatments was used with main effects of corn grain endosperm type (floury or vitreous) and fineness of grind (fine or medium). Rations included alfalfa silage, corn treatments, protein supplement, minerals, and vitamins and were formulated to contain 29% starch, 27% neutral detergent fiber, 18.2% forage neutral detergent fiber, and 18% crude protein. Corn grain treatments supplied 86.2% of dietary starch. Endosperm was 25% vitreous for the floury treatment and 66% vitreous for the vitreous treatment. The floury treatment increased rate of starch degradation by 94% (19.2 vs. 9.9%/h) and decreased rate of starch passage by 38% (16.1 vs. 25.8%/h), increasing apparent ruminal starch digestibility by 117% (53.7 vs. 24.7%). The floury treatment increased total-tract starch digestibility by 8% (92.2 vs. 85.1%) despite 37% lower postruminal starch digestion for the floury treatment compared with vitreous corn (38.4 vs. 60.7% of starch intake). Fine grind size increased apparent ruminal starch digestibility by 52% (47.2 vs. 31.1%) compared with medium grind size by increasing the rate of starch degradation by 105% (19.5 vs. 9.5%/h) with no effect on rate of starch passage. However, total-tract starch digestibility was not affected by fineness of grind because postruminal starch digestibility was 37% greater for medium compared with fine grind size (57.2 vs. 41.9% of starch intake). Endosperm type did not affect flow of nitrogen (N) fractions to the duodenum or microbial N efficiency, whereas fine grind size increased duodenal flow of nonammonia N by increasing duodenal flow of microbial N by 22% compared with medium grind size (438 vs. 359 g/d) but did not affect apparent total-tract N digestibility. No interactions were detected for any measure of starch digestion, ruminal N metabolism, or flow of N fractions to the duodenum. Endosperm type greatly affected ruminal and total-tract starch digestibility independent of the fineness of grind of corn grain with no effects on flow of N fractions.

Growth kinetics of Saccharomyces cerevisiae and tape yeast on the cassava pulp fermentation

Saccharomyces cerevisiae is the most commonly used yeast in the fermentation process on high starch/carbohydrate substrates, for example, cassava pulp, a by-product from the tapioca industry. In addition to the pure culture of S. cerevisiae, the fermentation process of cassava pulp can be done using tape yeast (a consortium of yeast, fungal and bacteria). The objective of this research was to study the growth kinetics of S. cerevisiae and tape yeast on cassava pulp fermentation. The growth kinetics of Saccharomyces cerevisiae and tape yeast was observed through cells number, rate of starch degradation, rate of dietary fiber degradation, rate of cyanide degradation, and rate of protein formation. The research showed that the S. cerevisiae pure culture could grow better during cassava pulp fermentation compared to tape yeast, which is reflected by the logarithmic growth rate (up to 72 h versus 48 h). The difference in the growth rate between S. cerevisiae pure culture and tape yeast will cause a difference in starch degradation rate (73.02 mg/h versus 65.09 mg/h), dietary fiber degradation rate (87.33 mg/h versus 21.09 mg/h), cyanide degradation rate (92.57.10−2 ppm/h versus 97.49.10−2 ppm/h), protein formation rate (48.92 mg/h versus 50.08 mg/h).

Performance of cellulose acetate propionate in polycaprolactone and starch composites: biodegradation and water resistance properties

Introducing starch into some polymers such as polycaprolactone (PCL) has been used to produce biodegradable plastics. The existance of a derivative of cellulose such as cellulose acetate propionate (CAP) with starch and PCL combinations might affect the degradation rate of starch when only mixed with PCL. To check whether this was the case, different investigations such as enzymatic degradation, composting trial and water resistance performance over a wide range of different compositions of such composites were studied. It is deducible that the use of cellulose acetate propionate can improve the performance of such composites without a big significantly changing their whole biodegradability. It was found that the presence of cellulose acetate propionate improved the water resistance properties which enable such composites to be used in the packaging industry.

Postharvest quality of ‘Brookfield’ apple field-treated with naphthalene acetic acid alone or combined with other growth regulators

ABSTRACT The Gala cultivars represent about 65% of the Brazilian apple production, however, it has a short harvest period, making necessary to use technologies that anticipate or delay fruit maturation. A widely used technology is the preharvest application of growth regulators. The objective of this investigation was to evaluate the effect of preharvest application of naphthalene acetic acid (NAA) combined with aminoethoxyvinylglycine (AVG) and 2-chloroethylphosphonic acid (Ethephon), on the quality of ‘Brookfield’ apple at harvest and after eight months controlledatmosphere (CA)(1.2 kPa O2 and 2.0 kPa CO2) storage followed by seven days of shelf life at 20 °C. The treatments were: [1] Control: application of water only; [2] NAA (40 g.ha-1); [3] NAA (40 g·ha-1) plus Ethephon (2.0 L·ha-1 24% of active ingredient), and [4] NAA (40 g·ha-1) plus AVG (0.83 kg.ha-1 15% of active ingredient). At harvest, fruit treated with NAA presented a higher level of starch degradation, ethylene production and respiration rate. Fruit treated with NAA plus AVG maintained better quality after eight months under CA storage plus seven days of shelf life, due to higher healthy fruit amount and higher flesh firmness, but this combination reduced the red skin color index. Additionally, NAA plus Ethephon may be an alternative to maintain the quality of ‘Brookfield’ apple during storage in comparison to the application of NAA isolated.

Role and mechanisms of callose priming in mycorrhiza-induced resistance.

Mycorrhizal plants display enhanced resistance to several pathogens. However, the molecular mechanisms regulating mycorrhiza-induced resistance (MIR) are still elusive. We aim to study the mechanisms underlying MIR against Botrytis cinerea and the role of callose accumulation during this process. Mycorrhizal tomato plants inoculated with Rhizoglomus irregularis displayed callose priming upon B. cinerea infection. The callose inhibitor 2-deoxy-d-glucose abolished MIR, confirming the relevance of callose in the bioprotection phenomena. While studying the mechanisms underlying mycorrhiza-induced callose priming, we found that mycorrhizal plants display an enhanced starch degradation rate that is correlated with increased levels of β-amylase1 transcripts following pathogen infection. Starch mobilization in mycorrhizal plants seems coordinated with the increased transcription of sugar transporter and invertase genes. Moreover, the expression levels of genes encoding the vesicular trafficking proteins ATL31 and SYP121 and callose synthase PMR4 were higher in the mycorrhizal plants and further boosted by subsequent pathogen infection. All these proteins play a key role in the priming of callose accumulation in Arabidopsis, suggesting that callose priming is an induced resistance mechanism conserved in different plant species. This evidence highlights the importance of sugar mobilization and vesicular trafficking in the priming of callose as a defence mechanism in mycorrhiza-induced resistance.