Bioconversion of bread waste by marine psychrotolerant Glutamicibacter soli strain AM6 to a value-added product: cold-adapted, salt-tolerant, and detergent-stable α-amylase (CA-AM21)

• Published in: Biomass conversion and biorefinery Vol. 13; no. 13; pp. 12125 - 12142
• Main Authors: Matrawy, Amira A., Khalil, Ahmed I., Embaby, Amira M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2023; Springer Nature B.V
• Subjects: Ammonium sulfate; Amylases; Bioconversion; Biotechnology; Bread; Detergents; Energy; Original Article; Renewable and Green Energy; Seawater; Stability; Washing powders; strain AM6; Halotolerant cold-adapted α-amylase; Bread waste; Eco-friendly low-cost effective approach; Detergent stable cold-adapted α-amylase; Liquid state fermentation; Psychrotolerant marine
• ISSN: 2190-6815; 2190-6823
• DOI: 10.1007/s13399-022-02325-3

The present work aims to exploit the zero-cost inducer bread waste (BW) for the production of cold-adapted α-amylase (CA-AM21) by the hyperproducer marine psychrotolerant Glutamicibacter soli strain AM6 EMCCN 3074. Incubation temperature (20 °C), incubation time, BW, (NH 4 ) 2 SO 4 , and modified seawater-based minimal medium were inferred to be significant factors influencing CAM-21 production in OVAT and Plackett-Burman investigations. BW (3.8%w/v), (NH 4 ) 2 SO 4 (0.098%w/v), and incubation time (2.329 days) prompted CA-AM21 (56.85 U/mL) with 7.58-fold enhancement, Box-Behnken design, and ridge steepest ascent path inferences. A two-step strategy was used to purify CA-AM21: fractional (NH 4 ) 2 SO 4 precipitation (60-80%) and a starch affinity chromatography. Specific activity, yield, and fold purification of purified CA-AM21 were 884.5 U/mg, 12.45%, and 285.3, respectively. CA-AM21 exhibited an approximate molecular mass of 14 kDa, deduced from SDS-PAGE analyses. The pH and temperature optimums for CA-AM21 were 7.0 and 40 °C, respectively. At 5–25 °C, full activity was maintained after 2 h. At pH 6.0–8.0, almost full activity (90–100%) was retained after 15 h. CA-AM21 demonstrated full stability after 30 min at 1.0–5.0 M NaCl, with 200% increased activity at 1.0–4.0 M NaCl. Full stability of CA-AM21 in the presence of non-ionic detergents, such as Tween 20, Tween 80, and Triton X-100, with 100% activity sustained after 30 min was retained. On soluble starch, purified CA-AM21 exhibited km and Vmax of 0.039 mg.mL −1 and 115.71 μmol glucose. min −1 . mg −1 , respectively. The purified CA-AM21 demonstrated remarkable significant washing efficiency with commercial laundry detergents thus implying its applicability for detergent formulations.