Abstract: Bacterial cultures are provided that comprise a modified Pseudomonas aeruginosa bacterium missing or deficient in two or more virulence factors. The two or more virulence factors can be selected from exotoxin A, hemolytic phospholipase C, phenazine-specific methyltransferase, alpha-1,3-rhamnosyltransferase, and 3-phosphoshikimate 1-carboxyvinyltransferase. Certain of the modified Pseudomonas aeruginosa bacteria are also missing or deficient in one or more alginate acetylation enzymes including the alginate Oacetyltransferases AlgI, AlgJ, AlgF, AlgX, and/or the C5-mannuronan epimerase AlgG. Methods of producing alginate are also provided along with compositions comprising alginate produced by the modified Pseudomonas aeruginosa bacteria.