BERLIN — Germany defied expectations yet again Tuesday, with a survey showing a record improvement in the economic outlook, despite the persistent threat posed by Europe’s sovereign debt crisis.

The Center for European Economic Research in Mannheim, a private research institute known by its German acronym ZEW, reported that its survey of economic sentiment among investors jumped 32.2 points in January from the previous month, to its highest level since July. It was the largest monthly gain in records going back to 1991, but still left the index at minus 21.6 points — deep in negative territory and well below the index’s historical average of 24.5 points.

“Contrary to repeatedly expressed fears of a recession, the assessment of the financial market experts gives reason for cautious optimism that Germany will only experience a dent in economic activity,” the ZEW president, Wolfgang Franz, said in a statement. He also noted that the European Central Bank’s huge infusion of money into the banking sector last month could have contributed to the uptick.

The institute’s economic expectations index for the euro zone also gained, rising 21.6 points to stand at minus 32.5 points.