الفهرس 
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Abstract
β–Gal have extensive applications in food, feed, pharmaceutical and medical industries. The present study deals with the production of β-Gal by certain thermophilic fungi locally isolated from soil.
The results obtained can be summarized as follows:
1- Five wild isolates were screened for β-Gal production, these are: Aspergillus niger, Chaetomium thermophile, Myceliophthora thermophila, Talaromyces thermophilous and Thermomyces lanuginosus. Only two isolates were chosen as potent producers. For β-Gal enzyme; Chaetomium thermophile and Thermomyces lanuginosus. Both are true thermophiles.
2- β-Gal production by the experimental fungi was optimized under Surface Culture (SC) conditions.
A-the optimum pH for β-Gal production was pH 5.5 for both C. thermophile and T.lanuginosus.
B-Maximal production of β-Gal was obtained at 45°C for both experimental fungi.
C-Maximal production of β-Gal was obtained after 7 days of incubation for C. thermophile and T. lanuginosus.
D-PGA (1.5%, w/v) was the best carbon source for β-Gal production by the two experimental fungi.
E-Casein (5.2%) was found to be the best nitrogen source for β-Gal production by C. thermophile and T. lanuginosus.
I- the optimized surface culture (OSC) medium for C. thermophile and T. lanuginosus containing (g L-1): 15.0, polygalacturonic acid; 5.2, casein; 1.0, K2HPO4; 1.0, MgSO4 and 0.01 FeSO4. pH 5.5, 200 CFU μL-1 and incubation at 45°C for 7 days, the β –Gal yield was 2.86 and 3.94 U mg-1 respectively.
3- In the second part of the study, the effect of solid substrate, culture (SSC) technique was investigated .the OSC solution in which the carbon was omitted was used as basal culture solution (OBS). The obtained results can be summarized as follows:
A-the best substrate was lupine-seed powder (LSP) at
moisture content (MC 50% ) for C. thermophile and T.
lanuginosus.
B-The best substrate loadage was (10.0 g) of lupine–seed Powder for both experimental fungi.
C-Maximal production of β-Gal was obtained after 7 days of incubation at 45°C for C.thermophile and
T. lanuginosus, SSC increased the enzyme activity about 10 folds for both experimental fungi.
D-The effect of some dairy by-products such as Lactose- Yeast extract (LY), cheese whey(W), Cane molass (CM),beet molass (BM),cheese whey (W) and cane molass (CM) (1:1), and Cheese whey (W) and beet molass (BM).on β–Gal production by the two experimental fungi was studied and the following results were obtained:
I- In case of C.thermophile ;the different media yielded the following β-Gal activities:
1-Lactose-yeast extract (LY) yielded protein content of (2.1 mg/ml) and enzyme activity of (18.3 U/ml).
2-Cheese whey (CW) yielded protein content of (1.5 mg/ml) and enzyme activity of (19.9 U/ml).
3-Cane molass(CM) yielded protein content of (2.8 mg/ml) and enzyme activity of (53.8 U/ml).
4-Beet molass(BM) yielded protein content of (2.3 mg/ml)
and enzyme activity of (25.1 U/ml).
5-Cheese whey (W) + cane molass (CM) (1:1) yielded
protein content of (2.2 mg/ml) and enzyme activity of
(58.2U/ml).
6-Cheese whey(W) + beet molass (BM) (1:1) yielded
protein content of (2.3 mg/ml) and enzyme activity of
(31.85U/ml).
II-While in T.lanuginosus; the different media yielded the
following β-Gal activities:
1-Lactose-yeast extract (LY) yielded protein content
of (1.54 mg/ml)and enzyme activity of (16.9 U/ml).
2-Cheese whey (CW) yielded protein content of (1.9
mg/ml) and enzyme activity of (11.9 U/ml).
3-Cane molass(CM) yielded protein content of
(2.6mg/ml) and enzyme activity of (50.3 U/ml).
4-Beet molass(BM) yielded protein content of (2.3
mg/ml) and enzyme activity of ( 27.2U/ml).
5-Cheese whey (W) + cane molass (CM) (1:1) yielded
protein content of (2.1mg/ml) and enzyme activity of
(57.2U/ml).
6-Cheese whey (W) + beet molass (BM) (1:1) yielded
protein content of (2.4 mg/ml) and enzyme activity of
(33.9 U/ml).
The highest activity was obtained on W/CM medium, followed by CM medium for both C.thermophile and T.lanuginosus. Growth of both experimental fungi on W/CM medium increased the enzyme activity to more than three folds than growth on LY medium.
The optimized SSC medium consists of 10 g LSP with 10 ml of optimized basal solution (OBS g/L): (5.2, casein; 1.0, K2HPO4; 0.5, KCl; 0.5, MgSO4.7H2O; 0.01, FeSO4.5H2O). Inoculation with 200 CFU ml-1 and incubation at 45°C for both experimental fungi after 7 days;
Crude enzyme (CE) was dialysed against 50 mM acetate buffer (pH 5.0) for both C. thermophile and T. lanuginosus. The crude enzyme dialysate (CED) was partially purified by ion exchange chromatography on bentonite (2.5%) and eluted and eluted with 0.1 M NaCl.
Some properties of partially purified β-Gal from C. thermophile and T. lanuginosus were studied and the following results were obtained:
A-the optimum temperature was 50°C and the enzyme was stable at a wide range of temperature (45-60 °C) for both fungi.
B-The optimum pH was 5.0 and the enzyme was stable at a wide range of pH (4.5-6.5) for both experimental fungi.
C-Alkaline metal ions Na+ and K+ in addition to divalent metal ions Ca2+ ,Co2+ ,Mg2+ ,and Mn2+; (5 mM);have no significant effect on the enzyme activity, while Hg2+ and Zn2+ completely inhibited the enzyme activity for both experimental fungi.
D-Treatment of the enzyme with the chelating agent EDTA does not affect the enzyme activity, indicating that the enzyme of C. thermophile and T. lanuginosus is not a metal requiring enzyme .PMSF and ME also had no effect on the enzyme activity, indicating that it is not a metalloprotein. No metal dependence in β-Gal of C. thermophile and T. lanuginosus