Raw Starch-Digesting Glucoamylase Production of Rhizopus sp. MKU 40 Using a Metal-Ion Regulated Liquid Medium.

Abstract

In this study we attempted to control some specified metal-ion concentrations in a liquid medium and found a highly raw starch-digesting glucoamylase (RSDG) producing culture with protease-less activity, which we have called a metal-ion regulated liquid medium. Rhizopus sp. MKU 40 could not grow and produce glucoamylase (GA) in the liquid medium without metal ions (SLS medium). The addition of iron, magnesium, and zinc ions in the liquid medium was essential to growth and GA production of Rhizopus sp. MKU 40. Calcium ions also stimulated its growth and GA production. To summarize, the addition of 75 ppm calcium ions, 2 ppm iron ions , 49 ppm magnesium ions, and 0.7 ppm zinc ion to the SLS liquid medium was the best condition for producing GA and resulted in a high specific activity of GA (21.9 U/mg protein). Specific RSDG activity of the crude enzyme was 5 .7 U/ mg protein, and the ratio of RSDG activity to GA activity was 0 .26. Since the purification was easy, the purification of GA was done in only two steps (ammonium sulfate precipitation and column chromatography on CM-Sephadex C-50). The enzyme was purified about 4 .8-fold based on specific GA activity with an 86.0% yield based on GA activity from culture supernatant. The enzyme was proved to be homogeneous as judged by SDS-PAGE, and it has a molecular mass of about 80 .4 kDa by comparison of its relative mobility on SDS-PAGE with those of standard proteins. For purified enzymes, the ratio of RSDG activity to GA activity was 0.16.

Extracellular amylase production of a thermotolerant Fusarium sp: isolated from Eastern Nigerian soil

“…Undefined starches are easily available and cheaper sources of starches in comparison to the more expensive industrially prepared starches. The present results showed that enzyme production was marginally pronounced when a combination of different metal salts was used which corresponded with the work of Morita et al (1999). The presence of organic nitrogen sources elicited a higher extracellular α-amylase by the Fusarium sp, which was also reported by Hernandez et al (2006).…”

Recent Advances in Microbial Raw Starch Degrading Enzymes

“…A-11 Ragi GA [42] Rhizopus sp. MKU 40 -GA [43] Rhizopus sp. W-08 Mildewed corn GA [44] Rhizopus stolonifer Cassava waste - [18] Synnematous sp.…”

Improving the Yield of Glucoamylase andα-amylase in Solid-state Co-culture

“…Glucoamylase activity was measured using the method described by Morita et al [18]. The reaction mixture for glucoamylase activity assay was composed of 1 mL of 2% (w/v) soluble starch (Nacalai Tesque Co., Kyoto, Japan) solution in 0.1M acetate buffer (pH 4.5) and 1 mL of the enzyme solution.…”