Reviewer response for version 2

Abstract

Barada River is characterized by an abundant growth of freshwater algae. Algae have been emerged as a new source for bioactive compounds, in this research Cladophora crispata was cultivated in the outdoor method, and algae sulfated Polysaccharides (SPs) were extracted by ultrasonic-assisted extraction methods. After extraction, Gel filtration was used to purify the crude SPs; SPs compounds were determined and selected and we investigated the effect of SPs as antibacterial agents. the purified extract gave two fractions (F1 and F2).  The chemical components of both crude and purified SPs were then determined. The highest carbohydrate content (74.12%) and protein content (4.02%) was found in the crude extract, while the highest sulfate content (12.17%) was found in F2, and the highest uronic content (18.46%) was found in F1. Fourier transforms infrared Spectroscopy (FT-IR) was used for confirmed that the crud and fractions consist of sugar, uronic acids, protein unite, and sulfate groups. Both  F1, and F2 was found to consist of rhamnose, galactose, xylose, and ribose based on the High performance liquid chromatography (HPLC) separation. Each fraction showed an inhibitory effect on the gram-positive and gram-negative bacteria. F2 has the lowest minimum inhabit concentration (MIC) value against Enterobacter aerogenes and Staphylococcus aureus; where its MIC values were  28 and 10 (mg/ml) respectively. Algae polysaccharides had the most important interest due to their antibacterial properties, which is makes them included in pharmacy and food applications.