[Ethereum] Send raw transactions using eth-lightwallet

I am creating a wallet app and trying to sign and send raw transactions using eth-lightwallet.

function functionCallWallet(){
        var fromAddr = document.getElementById('functionCaller').value
        var contractAddr = document.getElementById('contractAddr').value
        console.log("Contract Address:"+contractAddr);
        var abi = JSON.parse(document.getElementById('contractAbi').value)
        console.log(abi);
        console.log(typeof abi);
        var contract = web3.eth.contract(abi).at(contractAddr);
        var functionName = document.getElementById('functionName').value;
        var args = document.getElementById('functionArgs').value.split(",");
        var gasPrice = 50000000000
        var gas = 3141592
        txOptions = {
            gasPrice: gasPrice,
            gasLimit: gas,
            value: 10000000,
            nonce:2.0e20
            }
        txOptions.to = contractAddr;
        var functionCallTx = txutils.functionTx(abi,functionName,args,txOptions);
        var password = prompt('Enter password ', 'Password');
        lightwallet.keystore.deriveKeyFromPassword(password, function(err, pwDerivedKey) {
        var signedFunctionTx = signing.signTx(global_keystore,pwDerivedKey,functionCallTx,fromAddr);
        console.log("Signed function transaction:"+signedFunctionTx);
        console.log('');
        web3.eth.sendRawTransaction('0x'+signedFunctionTx, function(err, hash) {
            console.log(err);
            console.log(hash);
            });
        })
      }

I am able to sign the transaction correctly. But when it comes to sending the raw transaction on the network I am unsuccessful. In the web3 api they use https://github.com/ethereum/wiki/wiki/JavaScript-API#example-45
they use the ethereumjs-accounts library to serialize the raw transaction to hex. Does eth-lightwallet also have a serialize to hex function so that it could be used and then data is in format used by the web3 sendRawTransaction function or do have to use the ethereumjs-accounts library mentioned in web3 docs ?

I am getting this error, obviously I am not serializing it the correct way but I will put the error anyway

Error: rlp: input string too long for uint64, decoding into (types.Transaction)(types.txdata).AccountNonce
    at Object.module.exports.InvalidResponse