January 13 (SeeNews) - Croatian hotel operator Maistra [ZSE:MAIS-R-A], a unit of diversified conglomerate Adris Grupa [ZSE:ADRS-R-A], plans to invest 1.4 billion kuna ($215.2 million/182.2 million euro) by 2017 in a bid to upgrade most of its properties to four- and five-star category, the parent company said on Tuesday.