Disclosed are compositions and methods directed to environmentally friendly, starch-based adhesives with improved properties and adhesive additives which improve the properties of existing starch-based adhesives. Some embodiments are directed to compositions comprising: a starchbased cross-linked phenolic heteropolymer; a plurality of antimicrobial agents covalently bound to the starch-based cross-linked phenolic heteropolymer; and a plurality of sugar units covalently bound to the starch-based cross-linked phenolic heteropolymer. Some embodiments are directed to modified starch-based adhesives comprising: a starch-based adhesive and an additive, the additive consisting of a starch-based composition comprising a starch-based cross-linked phenolic heteropolymer; a plurality of antimicrobial agents covalently bound to the starch-based cross-linked phenolic heteropolymer; and a plurality of sugar units covalently bound to the starch-based crosslinked phenolic heteropolymer.