CHICAGO, June 16 (Reuters) - Spot soybean basis bids turned lower on Monday as buyers protected themselves against rising futures prices, analysts said.

• Soybean bids fell at an elevator, two processors and two river terminals.

• Corn bids were slightly mixed. The corn basis rose at an Illinois processor and decreased at an Indiana ethanol plant.

• Falling basis values also reflect expectations for a large autumn harvest and weak demand that has eroded processing margins for companies that crush beans into soymeal livestock feed and soyoil used for cooking and producing biofuels.

• Soyoil, a feedstock for biodiesel fuel, gained support after the EPA proposed last Friday to increase the amount of biofuels that oil refiners must blend into the nation's fuel mix over the next two years. The proposal exceeded trade expectations.

• Chicago Board of Trade soybean futures surged in the overnight session but later pared gains. July soybeans SN25 were last up 1 cent to $10.68 per bushel around midday.

• CBOT corn futures were last down 9-1/2 cents to $4.35-1/4 per bushel.

Basis values are quoted against CBOT futures in cts/bu:

NOTE: 0 = Option price, UNC = Unchanged, UNQ = Unquoted

NC = Not comparable, DP = Delayed price, N/A = Not available,

F = January, H = March, K = May, N = JulyQ = August, U = September, X = November, Z = December

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LINKS: 0#USCSHGRN-PM

For U.S. forward basis spreadsheets, please click:

CORN/BASIS, SOYA/BASIS, WHEAT/BASIS, MILO/BASIS

- CBOT corn report COR/

- CBOT soybean report SOY/C

- CBOT wheat report WHE/C

- U.S. grain barge freight values BG/US

- U.S. Midwest cash grain PM GRA/PM

- U.S. CIF/FOB Gulf Grain GRA/F

(Reporting by Heather SchlitzEditing by Rod Nickel)

((Heather.Schlitz@thomsonreuters.com;))