Apple pectin

Figure 12. Binding of calcium ions by pectate and apple pectin, measured by equilibrium dialysis gainst citrate to buffer the concentration of free calcium ions at low levels.

For more details about the sensory properties of the pectin preparations additional sizes such as thixotropy and viscosity have to be referred to (see figure 6). Fruit preparations with apple pectin Classic AY 901 have a relatively high yield point after shearing, a small thixotropic area, and a relatively high viscosity. This supports the statement, that their texture is weakly elastic and highly reversible. The apple pectin Classic AY 905 gives products with a sufficiently high yield point at 35 % soluble solids and a pronounced area of thixotropy. 

To improve production of rhamnogalacturonase by Aspergillus aculeatus CBS 115.80 shake flask ejqjeriments were performed on several substrates. Cross reactivity was found after transfer to thamnose in combination with galacturonic acid and on apple pectin, citrus pectin, beet pectin and sugar beet pulp. No cross reactivity was found after transfer to meda containing simple carbon sources such as sucrose, glucose, fiuctose, rhamnose or galacturonic acid. 

A.aculeatus CBS 115.80 was grown on apple pectin in a fermenter and strong induction of Rgase production could be observed. Total RNA was isolated from such an RGase producing culture and used for the construction of a cDNA library. 

Influence of some cations on the reaction of apple pectin with ammonia in homogeneous media... 

The running of parallel reactions of hydrolysis, ammonolysis and depolymerization of apple pectin in aqueous solution of ammonia (IM) at 25 C were investigated. It was examined the effects of monovalent cations (Na, K", NH4 ) and divalent cations (Ca, Mg ) when they were added as chloride salts. It was found that the relative rates of the above mentioned reactions, depend on the nature and concentration of the added salts as well. The chlorides of sodium, potassium and calcium accelerate hydrolysis and depolymerization, while magnesium chloride delays these reactions. Ammonolysis was increased in cases of ammonium chloride addition. 

In the present investigation we set before ourselves the task to check the influence of chlorids of different alkali and alkali-earth metals on the rate of the hydrolysis, ammonolysis and depolymerization of apple pectin in aqueous solution of ammonia. 

Here data on apple pectins are presented. A comparison of corresponding data on apple and citrus pectins will be given in a future paper. 

The terms for the purified apple pectins indicate the degree of methylation. 

For cultures on pectin, 1 ml of grown cells for three days on glucose, were transfered to fresh inorganic salts medium with 0.5% (w/v) pectin (apple pectin, Fluka) and grown for six days. 

Total RNA was isolated from mycelia cultured 6 days on PG-inducing and non- inducing conditions (apple pectin and glucose, respectively). The RNA extraction was performed according to the phcnol-SDS method combined with selective precipitation using LiCl. RNA concentration was estimated by absortion at 260nm. 

Polygalacturonases were strongly induced in FORL by apple pectin, citric pectin and polygalacturonic acid. When FORL was grown on ucose as carbon source no extracellular PG activity could be detected. Galacturonic acid did not look like a good inducer of PG since the increase of enzyme activity was delayed in comparison with the other carbon sources, after the 5th day of incubation, and also showed lower values (fig.l). 

Figure 1. Time course of PG-production by FORL in culture media containing apple pectin (o), citric pectin ( ), polygalacturonic acid (o), monogalacturonic acid Of), glucose (/ ) and sucrose ( ).

Since the best inducer for the polygalacturonase activity was apple pectin, the experiments analyzing expression were made in this conditions and as with glucose PG-activity could not be detected, it was used as control. 

Figure 2. SDS-PAGE of a six days old culture. Lane 1 and 6 molecular mass standard, lane 2 and 4 apple pectin culture medium, lane 3 and 5 glucose culture medium. Lanes 2 and 3 to isolates ru, lanes 4 and 5 to isolates T2. ...

Figure 4. In vitro translation pattern of RNA. Lanes 2 and 4 from apple pectin...

The second experiment was carried out with the same RNA isolated from mycelia growing on presence of glucose and apple pectin. cDNAs were obtained from those RNA by reverse trancription and used as template for PCR assays. Specific oligonucleotide primers for PG gene were used in the amplification reaction. The Fig-5 shows the results of this amplification experiment. 

Figure 5. 1% agarose gel showing PCR amplification products for PG cDNA obtained from mRNA isolate. Lanes 1, 2, 4 and 6 apple pectin culture medium, lanes 3, 5 and 7 glucose culture medium, lanes 1, 2 and 3 to isolate r,3 and lanes 4, 5, 6 and 7 to isolate rz. Lane 8 corresponds to the amplification of the 742 pb probe cloned in the vector PCR TM (In-vitrogen) digested with Eco R1 and lane 9 A digested with Pstl. 

Figure 5A,B. Northern analysis of an A. aculeatus multicopy transformant (A) compared to the wild type (B). RNA was isolated from the mycelium before (lanes 1), 6 h after (lanes 2) and 24 h after (lanes 3) transfer of the corresponding strains to minimal medium (MM) with 1 % apple pectin. The location of the rhgA transcript is indicated with an arrow.

Colquhoun IJ, Ruiter GA de, Schols HA, Voragen AGJ (1990) IdentiHcation by n.m.r. spectroscopy of oligosaccharides obtained by treatment of the hairy regions of apple pectin with rhamnogalacturonase. Carbohydr Res 206 131-144... 

Degree of pectin metoxylation is the main factor that determines the pectinesterase action. Lemon pectin was hydrolyzed most easily among all pectin studies the speed of methanol release was 2.02 M 10 min.. This is accounted by the fact, that the degree of the lemon pectin metoxylation is higher than in case of beet and apple pectin. All above mentioned shows, that pectinesterase from P. fellutanum possesses specificity towards lemon pectin (Figure 3). 

Nitric acid is less commonly used for hydrolysis, but, in combination with urea, has been recommended for polysaccharides containing uronic acid residues28 and it has been used in a study of apple pectin.29... 

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