title: A new raw-starch-digesting α-amylase: production under solid-state fermentation on crude millet and biochemical characterization.
abstract: A new Bacillus strain degrading starch, named Bacillus sp. UEB-S, was isolated from a southern Tunisian area. Amylase production using solid-state fermentation on millet, an inexpensive and available agro-resource, was investigated. Response surface methodology was applied to establish the relationship between enzyme production and four variables: inoculum size, moisture-to-millet ratio, temperature, and fermentation duration. The maximum enzyme activity recovered was 680 U/g of dry substrate when using 1.38 × 10(9) CFU/g as inoculation level, 5.6:1 (ml/g) as moisture ratio (86%), for 4 days of cultivation at 37 degrees C, which was in perfect agreement with the predicted model value. Amylase was purified by Q-Sepharose anion-exchange and Sephacryl S-200 gel filtration chromatography with a 14-fold increase in specific activity. Its molecular mass was estimated at 130 kDa. The enzyme showed maximal activity at pH 5 and 70 degrees C, and efficiently hydrolyzed starch to yield glucose and maltose as end products. The enzyme proved its efficiency for digesting raw cereal below gelatinization temperature and, hence, its potentiality to be used in industrial processes.
authors.affiliation: National school of engineering, Unit enzymes and bioconversion, Route de Soukra km 4, 3038 Sfax, Tunisia.
authors.forename: Sameh
authors.initials: S
authors.lastname: Maktouf
authors.forename: Amel
authors.initials: A
authors.lastname: Kamoun
authors.forename: Claire
authors.initials: C
authors.lastname: Moulis
authors.forename: Magali
authors.initials: M
authors.lastname: Remaud-Simeon
authors.forename: Dhouha
authors.initials: D
authors.lastname: Ghribi
authors.forename: Semia Ellouz
authors.initials: SE
authors.lastname: Chaabouni
mesh_terms: D001407:Bacillus / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D002452:Cell Count; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008320:Maltose / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D008897:Panicum / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013213:Starch / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D000516:alpha-Amylases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D008320:Maltose; D013213:Starch; D000516:alpha-Amylases; D005947:Glucose