Abstract
Pectate lyases play an essential role in textiles, animal feed, and oil extraction industries. Pichia pastoris can be an ideal platform for pectate lyases production, and BspPel (a thermo-alkaline pectate lyase from Bacillus sp. RN1) was overexpressed by combined strategies, reaching 1859 U/mL in a 50 L fermentator. It displayed the highest activity at 80°C, and maintained more than 60% of the activity between 30 and 70°C for 1 h. It showed an optimal pH of 10.0, and exhibited remarkable stability over a wider pH range (3.0-11.0), retaining more than 80.0% of enzyme activity for 4 h. The Km and kcat of BspPel on PGA (polygalacturonic acid) was 2.19 g L–1 and 116.1 s–1, respectively. The activity was significantly enhanced by Ca2+, Mn2+, and Cu2+, and a slight increase was observed with the addition of Ba2+ and Mg2+. Scanning electron microscope was used to show the degumming efficiency of BspPel on ramie fibers. The loss weight was 9.2% when treated with crude enzyme supernatant and 20.8% when treated with the enzyme-chemical method, which was higher than the 14.2% weight loss in the positive control treated with 0.5% (w/v) NaOH alone. In conclusion, BspPel could be a good candidate for the ramie degumming industry.
Highlights
Pectin, an ubiquitous structure constituent of the middle lamella and the primary cell wall in the plant (Soriano et al, 2006), is a heteropolysaccharide composed essentially of long chains of α1,4-D-polygalacturonate, which are partially methyl esterified (Van Truong et al, 2001)
Alkaline Pels are desired for removing the pectin from ramie, since pectin is more soluble in alkaline solution
ANS59493.1) (Zhou et al, 2017a) with 98% identity, indicating that Bacillus sp. RN1 pectate lyase (BspPel) belongs to the PL1 family
Summary
An ubiquitous structure constituent of the middle lamella and the primary cell wall in the plant (Soriano et al, 2006), is a heteropolysaccharide composed essentially of long chains of α1,4-D-polygalacturonate, which are partially methyl esterified (Van Truong et al, 2001). Ramie fibers have gum material (20–35%), which contains pectin and hemicellulose, hindering its application. It is important to remove the pectin when processing the fiber. The enzymatic degradation of pectin requires the combined action of several pectinolytic enzymes with different methods of action (Jayani et al, 2005), and this enzymatic methods can efficiently remove ramie gum under mild and flexible conditions and serve as a good alternative to conventional degumming methods, with decreased environmental pollution, less damage to the fibers and improved yield and quality of degummed ramie (Zhang et al, 2013; Zhou et al, 2017a). Alkaline Pels are desired for removing the pectin from ramie, since pectin is more soluble in alkaline solution
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