MADRID, June 30 (Reuters) - Singapore"s wealth fund GIC agreed to invest around 1 billion dollars in Biomat, a U.S.-based plasma collection company owned by Grifols (GRLS.MC), thus becoming a strategic investor in the Spanish pharmaceutical company, Grifols said on Wednesday. GIC will have a minority stake in Biomat USA, which has a network of 296 plasma collection centres in the United States through the acquisition of newly issued non-voting shares. The company didn"t disclose the stake GIC will taking in Biomat. Barcelona-based Grifols will use proceedings to reduce debt, which at the end of March stood at 6.2 billion euros ($7.38 billion). Grifols shares were up 1.5% in early trading, while benchmark Ibex-35 was down 0.7. The company is valued by the market at 13.5 billion euros. ($1 = 0.8403 euros)