November 23 (SeeNews) - Shares in Bulgarian cellulose producer Svilosa [BUL:3MZ] gained 6.0% to 5.3 levs on the Sofia bourse on Friday, after the company announced that A.R.U.S. Holding has sweetened its buyout bid for the remaining 6.74% stake in the company it does not already own to 5.5 levs per share.